82% is the grade for Bethsoft's Knights of the Nine in a review at Just RPG:

 Your journey to find these relics will take you all across the map and into some really interesting dungeons. Some of the dungeons are fairly long, while others are very brief. I was actually surprised by some of the puzzles in the dungeons because they seemed fairly creative and at times a bit challenging. However, the rewards are well worth it because the relics you collect will prove to be very formidable. Every good faction needs a place to call home, so you'll also be able to take over the priory of the nine and make it your own. Other Knights will also hear of your quest and seek to join you. These Knights will help you during your adventure and fight beside you in the final confrontation! Your journey will allow you to explore new dungeons, find new weapons and equipment, battle new enemies, and meet new people. If you've played through any of the Guild quests in Oblivion, then you sort of know what to expect out of Knights of the Nine. It’s worth noting that the additions in Knights of the Nine aren’t anything drastically different from what we’ve already seen in Oblivion. So, if you’re expecting an entirely new game, then you’ll surely be disappointed. However, “more of the same” isn’t a bad thing when you’re talking about a game like Oblivion.

In their longest review in nearly a year, GamerDad details all of the modules making up the retail package for the Knights of the Nine content pack.  The final score is a below average 3/5, with criticisms similar to the following:

Mehrune's Razor: Now *this* is a quest! A huge dungeon full of atmosphere and interesting areas and loads of enemies. Unfortunately it is also littered with every other problem that plagues Oblivion - scaled enemies, scaled drops and scaled chests. It is a sort of cognitive dissonance - you are working your way through a nicely designed and atmospheric dungeon that is mostly empty and contains a bunch of enemies that are easily defeated. All of this for a single excellent weapon and a decent armor set that you will probably just sell since you already have something better. I was very disappointed with this module - such a great dungeon full of possibilities left unrealized in a sea of scaled blandness. Had it presented an actual challenge and more than a minor reward it would have been worth purchasing by itself. 

An incredibly brief review of Knights of the Nine is up at Games Radar, with a score of 8/10.  Here's the main substance of the article:

There are no extra lands to explore here (boo!), but you do get to roam Cyrodiil in search of Wayshrines, meet with Pelinal Whitestrake and reinstate a legendary religious order before banishing dark sorcerer Umaril back into the abyss. There’s also a dangerous new foe in the shape of the Aurorans and some sweet new weaponry and armor. Knights of the Nine isn’t in the same league as stellar Morrowind add-ons like Tribunal and Bloodmoon but any fresh reason to revisit the world of Oblivion once again is all right by us…

AtomicGamer has awarded 78% to Bethsoft's Knights of the Nine, despite lamenting the value compared to some of the quality community mods available.  Here's a snip on the new quest line:

As you go through Knights, you'll notice that there aren't really any new technical tricks or the like here.  As with many of the factions and downloaded add-ons, you'll get your own stronghold to use in the process of rebuilding the order, and you will even get the chance to bring a Knight with you into battle - whether it's to further the Knights or to work on other quests out in the world.  While Oblivion doesn't have the classic "Paladin" seen in many RPGs, these holy knights are about as close as you can get.

With the press continuing to confuse Bethsoft's Knights of the Nine addon for a full-blown expansion, GamePro has a review with a score of 4.25/5:

The basic plot involves the player finding, putting to rest and then rebuilding the order of the Knights of the Nine in order to vanquish a returned evil being. This is accomplished by collecting each of the various parts of the Armor of the Crusader, which is required to defeat said evil. It's a well told story, partially due to the newly voiced dialogue and characters, which matches the same high quality that was found in the original.

Bethsoft's latest Oblivion addon, Knights of the Nine, has been reviewed at Game Industry News.  Despite some criticism of the scope and length, the score is a full 5/5.  Here's the conclusion:

As expansion packs go, I was both impressed and slightly disappointed with this one. I kind of expected something on the order of Bloodmoon, which offered what amounted to an entirely new game for Morrowind. Knights is nice, but getting finished in just six hours left me wanting more. If you have a PC, do yourself a favor and buy the full retail game box so at least you will have a bunch of extra content to play with as well as the Knights quest. Either way, Knights will inject some real life into Oblivion for you, especially if you have started to wander off and play other titles.

CVG has a short, sweet review of ES4: Knights of the Nine. Handing over a lukewarm score of 7.4, the reviewer said:

Good as it all is, we're not sure if this lot is worth £20. The problem is that most of the downloadable content is aimed at specific character types: a pure combat character probably won't give a stuff about spell tomes or a Wizard's tower, while the average mage will find the powerful new quest items totally useless. You're far better off just choosing the content you want online, and this works out a hell of a lot cheaper too, even if you buy everything (£12). Is it really worth an extra £8 to own a box and a disc?

An enthusiastic review of Knights of the Nine is online at Grrlgamer.  There's no score but their opinion is obvious:

An already outstanding game is made even better through this ten hour quest which explores another aspect of the vast and fascinating world of Tamriel. If you've come to play through the rest of Oblivion, I command you, download Knights and add to your experience. It is quite worth it, if only to rediscover what you originally loved so much about Bethesda, and why we must keep them in our hearts and thanks during this Holiday Season. 

Knights of the Nine has been reviewed at GameZone.  The score is 8.5/10 and here's a bit on the story:

While past downloads point out the new content, the Knights quest line is inserted into the game’s universe so gamers can take up the quest at any point they wish. The quest is centered in the township of Anvil where you will discover that the Chapel of Dibella has been desecrated and many of the priests have been murdered. Just outside, a man raves that the end is near and once you start talking to him he reveals to you that a wicked servant of evil who was banished to Oblivion has somehow been resurrected and if nobody stops him he could very well threaten the entire realm. So it is up to you to stop this immoral named Umaril and to do so you must journey onward just beyond Cyrodill in order to locate the armor and weapons of the Divine Crusader and thus reclaim the glory of the famed Knights of the Nine.

The reviews for Elder Scrolls IV: Oblivion - Knights of the Nine are pouring in, naturally. GameZone just published their review, giving it a respectable 8.5/10. 

If you love Oblivion or want to add another interesting component to this already rich gaming experience, Knights of the Nine for the PC will definitely not disappoint in the very least.

The British gaming site Pro-G just published their review of Elder Scrolls IV: Oblivion - Knights of the Nine, giving it a near perfect 9/10. They sited the game's graphics, sound and puzzles as its high points, and generic dungeons and odd voiceovers as its minor lows.

Given your avatar's snazzy new wardrobe, base of operations, minions and the righteous euphoria associated with being a force for good, The Knights of the Nine is well worth the 800 Microsoft points or bargain price on the PC. This quest line is the biggest yet and keeps you hooked right to the end. While the dungeons are not as big or as maze-like as the previous expansions, the chance to really explore Cyrodiil really makes this quest much more effective and allows for a greater appreciation of the graphical tweaks and new locations. Download it now!

bit-tech.net has just published their review of Elder Scrolls IV: Oblivion - Knights of the Nine. They scored it well with a 8/10, proclaiming that the expansion is a must have for any hardened Oblivion fan.

All in all I felt this expansion/additional content disc is well worth the money if you're a big Oblivion fan. The additional content slips straight into your game and works seamlessly, so no requirement to start a new game or anything silly like that. As such, it's really hard to complain. There is almost certainly over 6 hours of playable content here as well as new additions that will add depth to the original game.

My only problem with this is that there probably isn't enough to entice you're average Oblivion fan out of retirement. A lot of the quests are specific to certain types of character. Where an expansion pack will tend to cater for everyone with a few more hours of play, the impact these mini expansions will have on you is completely dependant on what type of game you like to play.

Knights of the Nine has been reviewed at Killer Betties, with a score of 4/5:

The big thing about the Knights of the Nine content is what exactly makes up the title – Knights of the Nine. In the new content, you'll find yourself taking up the quests the original Knights of the Nine once held, and find yourself reestablishing their sacred order and becoming the head knight and amassing your own troops to follow you. It's fun to go through the game and discover people throughout the content's journey who want to join up, but the knights are pretty wasted and only used in the final moments. Still, the priory is nice and really starts to look pretty spectacular as you garner troops.

Knights of the Nine for the PC has been released through OblivionDownloads and should also be available in stores, catching up with the Xbox 360 version released a week or so back.  Here's their description:

A fallen King has been unchained from the darkness of Oblivion to seek vengeance upon the Gods who banished him. Only a champion pure of heart can vanquish the evil that has been released upon the land. You must heed the call, reclaim the lost relics of the Divine Crusader, and return the Nine to glory. New dungeons, characters, quests, and mysteries await.

Knights of the Nine has been reviewed at Gameplay Monthly.  The score is 'A-' and apparently this content includes some non-linear questing:

Don't worry though, the rest of the quests in Knights of the Nine are not tedious at all. The rest of the quest-line includes item gathering which may not seem so exciting at first glance, but upon doing these quests, this is not the case. These quests are by far the best in the game, for they are not the linear dungeon crawlers you have done over a hundred times now, they are truly complex and require some thought put into them. For example, one quest tests your patience in combat; another is a series of riddles that open new path. These are nothing like those boring Fighter's Guild quests.

Eurogamer has served up a short review of Bethsoft's latest Oblivion addon, Knights of the Nine.  The score is 8/10 and here's the interesting opening:

Oblivion divided opinion. Released in March to rapturous applause, it seemed as though Bethesda had driven Western RPG standards to new heights. Presented with a seemingly overwhelming array of choices, dwarfed by an enormous land to explore, besotted by lavish detail and beauty - Oblivion appeared to be the Goliath we'd been waiting for. Critics opened their arms and welcomed what they saw as the first of the truly next-generation games.

Yet it seems one person's selling points were another's drawbacks. Overwhelming choice was narrowed to dull repetition, vast lands became laborious obstacles, and beauty was criticised for her performance. Apathy soon crept in, attentions turned elsewhere. Could it be that this pinnacle of gaming lacked the depth to engage, was it guilty of having no soul?

Knights of the Nine has been released via Xbox Live and will follow for the PC on December 4th:

Knights of the Nine is now available for download on Xbox Live. The Knights of the Nine collection is in stores now, which includes Knights of the Nine plus all other downloadable content released to date. Knights of the Nine for PC will be available to download Dec. 4 on OblivionDownloads.com.

Elder Scrolls.net dropped us a line to say they have 20 new screens from the retail version of Knights of the Nine.

A hands-on preview of Bethsoft's upcoming Oblivion addon Knights of the Nine is up at GamerNode:

Knights starts out with an attack on Anvil's Chapel of Dibella. When you venture there, you'll meet a prophet who foretells a prophecy of an ancient evil (named Umaril) arising from the past to lay waste to all who oppose him. But in order to combat him, you'll need to acquire the equipment from the legendary warrior who laid the smack down on him back in the past. Note this quest-line is only for good folks, but that doesn't mean you evil folks are immediately ruled out.

IGN has posted a preview of Oblivion's upcoming Knights of the Nine addon:

It seems an eldritch evil named Umaril, an Ayleid Sorcerer-King, has started causing trouble again. More specifically, he's responsible for murdering the clergy of Anvil's chapel. After speaking with a rather energetic prophet on the streets of Anvil a questline kicks off sending you to nine shrines across Cyrodiil. Along with the quest you get a map that marks all the shrines' locations. Though fast travel isn't possible, the spots are easy enough to get to even if you're just starting a new game.

Bethesda's Pete Hines just dropped us this info regarding the upcoming expansion for Oblivion:

First, I wanted to clarify a couple things on Knights of the Nine. The retail version of Knights of the Nine is a collection (for PC) that includes Knights of the Nine plus all the other DLC released to date. That’s why it’s $19.99. If you want just Knights of the Nine for PC, you can download it for $9.99 and get just that DLC without the rest of it. Same on 360…800 points for just Knights of the Nine. A retail version for 360 isn’t technically feasible at this time. If/when it becomes a possibility we’ll let folks know; it’s certainly something we’d like to offer. Release date for Knights of the Nine is 11/21 for the retail version as well as the 360 version on Xbox Live. It will be available to download for PC (from www.obliviondownloads.com) on 12/4.

Killer Betties has an interview with Bethsoft's Pete Hines on Knights of the Nine:

3. For fans who have already gobbled up that content, there is still new content coming they haven't played yet such as an "all-new faction and quests for noble characters." What is this new faction called and what are they about? Good? Evil? What types of goals will you be accomplishing in this faction?

The new faction is basically the opposite end of the spectrum from the Dark Brotherhood. So you have this really evil faction in Oblivion, but there's no really good guys. No noble knights going out to do good and protect the innocent and all that. So you basically get to restart an order of holy knights that has been defunct and is now needed to help fight this sorcerer-king that has shown up and is causing problems.

Bethesda has opened a product page for Knights of the Nine, the upcoming Oblivion expansion. Not much new info there though except a few screenshots.

Bethsoft has kicked up a Knights of the Nine wallpaper with their latest newsletter, available in 640x480, 1024x768, 1280x768 and 1600x1200 resolutions.

New info on the release of the Oblivion addon "Knights of the Nine":

Bethesda will release the addon for PC & Xbox360 versions on november 21st in the US. The addon contains the new quest "Knights of the Nine" from the PS3 version.

In Europe, Ubisoft will release the addon in stores on november 23rd (at least for Germany), while you can also download the extra content via www.obliviondownloads.com.

The retail version (approx. 20 US$) will also contain the the other releases Horse Armor, The Orrery, Wizard’s Tower, Vile Lair, Thieves Den, Mehrunes’ Razor and Spell Tomes.