I've reached level 39, finished the main quest, finished the mage's guild quest, decided the civil war (all some levels ago) …and now I'm horribly bored. I'm not sure how people maintain the desire to continue playing if there is no driving imperative i.e save the world! or Save the Empire! I'm also noticing things that didn't bug me before - like repetitive barrow/cave design (esp the traps and puzzles they use), the same kinds of enemies, the same (often inane) NPC conversations … in fact no new or interesting enemies have surfaced - seen them all (or so it appears - well, I now get hassled by 'elder dragons' … whoop dee doo). I also feel that the majority of quests are really 'fedex' - some are done in a few minutes if you fast travel. Looking back, I think the number of interesting quest-lines was pretty low, certainly as a proportion of the total set of quests I completed.
Still, I did get a good 85+ hours out of it (I tend to play games somewhat obsessively till I'm done), so I'm certainly not feeling cheated - it just seems a shame that there is so much left of the world (40%?), and I have no desire to go exploring, since I expect that 9/10 times I'll find something very similar to what I've already experienced. What would be really nice is to have some 'epic level' quest line that kicks in once the main quest is done, and you're a certain level - that would give you a reason to want to stay. I know - that will probably be DLC. I also seem to have missed any daedric items - well, except the ones given out by the daedra quests. I assume these start getting dropped at even higher levels?
I hope that future DLC also adds back spells that they removed - like water walking and Open Lock (pretty please). In fact, the loss of spell making and the removal of nasty spells like weakness to X etc really made the magic system poorer. I suppose people power gamed that - but they always do that anyway. It could have been rebalanced. Anyway, lets see what the future brings.