Only two complaints so far about Oblivion. One is that the the face gen is a little too realistic making most faces in the game look like they've been bashed in with an ugly stick. Other complaint is that the ability wheel is not shown on the screen meaning I have memorize which number key I put all of my action/spells. For a magic using character its a serious pain to have to remember that I put my fireball spell as key '4' instead of say a healing spell while in the middle of a fight.
The only other complaint was not being able to sell stolen items but they've just created a mod to fix that
I haven't noticed any glitches yet really. Awesome game!