On the technical side I haven't much to complain. I think I've encountered two CTDs in quite a lot of hours played, so that's nothing truly massive.
Have gotten stuck once, which - given the size of the world and the endless possibilities for stuckiness to appear - isn't too bad either.
Corpses have a certain habitus of bobbing and splashing on the water all the time, which is slightly disturbing and bloddy annoying.
Bugs, yes, there are some out there. I've made it a habit to quicksave before enchanting, because I had it happen way too often that after enchanting 29 iron daggers I end up stuck on the screen. Sometimes saving and reloading that save helps getting unstuck, sometimes not.
Quest dialogues that get screwed up and make some quests impossible to complete or start happend to me once or twice, too, which is pretty damn annoying.
Imbalances: The "levelling the wrong stuff" has the possibility to hurt, but then there's not much that doesn't help you in combat in one way or the other ( Speech comes to mind ). I haven't had much problems there. Also sneak on my khajit is working perfectly. It does get cheesy sometimes when you sneak up to someone, stab him twice, then run away through half of the dungeon until he looses you, only to repeat that two or three times more. However, I'm glad that I can loose enemies by running away and hiding, even if it's a bit unrealistic from time to time. Also a bit weird: Fire sneakily an arrow at someone. Miss it, and have the arrow hit the wall two feet behind him. See the enemy stare at that wall for 10 seconds, figuring what has happened. Overall the AI has improved massively from Oblivion but as you expect it, it's still miles away from being perfect - which is an impossible task anyway.
I have a gripe with some imbalanced perk trees, mainly with smithing. Heavy dragon armor is weaker than deadric - okay, it's at least easier to get. But I dislike massively that the 'light armor' smithing tree only offers the third best weapons.
Overall it is a nice gaming experience. Although I'm having a lot of fun with playing different characters ( and pursueing different goals ) over playing one super-character that does everything.