Mass Effect 2 - Previews @ Lost Gamer & GamePro

The Lost Gamer has spoken to Casey Hudson, ME2's Project Director. They've learned a lot about Bioware's improvements for ME2. Here's the info about how the overheat system has been changed:

The weapon overheat system has also been modified, with the team noticing that in Mass Effect players would overheat their weapon and then be stuck with what to do for a few seconds. Therefore, within the second title they aimed to making everyhing seem more fluid by reducing the charge time on powers too with Hudson saying "So now you can fire powers much more frequently and have a lot more fun on the battlefield. In terms of the overheat and ammo, our goal then became to be able to add that tension and resource consideration to combat, again as part of getting to the best gameplay we could, while retaining the idea that the Mass Effect universe established.

GamePro also has a preview of ME2 up at their site. They talk about their hands-on experience with ME2, focusing on playing through Illium, the Asari Colony - they also meet Samara, the new playable NPC:

As soon as the mission began, we were given a directive to track down Samara, a dangerous and much-talked-about Justicar (essentially the equivalent of a Spectre) who provides a stark contrast from the peace-loving and gentle-natured Asari that we're familiar with in Liara T'Soni. Apparently, Samara was a dark legend among the Asari, known as a ruthless combatant whose mere name seemed to make the local population start breaking out in nervous sweats. Luckily for us, that's exactly the kind of crewmember that Commander Shepard's been looking for to take out the Collectors that have been harvesting humans. Glancing at a nearby police barricade, we could tell that she was probably in the area.