I'm kind of disappointed by Diablo 3's performance on my machine. I run on max settings at 1900x1028 and seem to be getting slight stutters whenever entering combat or using special attacks.
I like to think my machine has enough horsepower to handle this game.
8gb DDR3 1600
ATi 7950 (900/1250)
Fully updated drivers.
I've tried turning shadows all the way down as shadows usually hit games the hardest, but no luck. The strange little micro lag still happens.
Maybe it's the nature of a beta that isn't fully optimized for drivers yet?
Diablo 3 beta is currently trying to load animations and things on the fly, which is no good. It's not caching certain things, which is why it's only when using a special move or entering combat. If you play long enough, you'll see that it starts to go away as more and more animations load while playing. It's a bug.
I've been experiencing the same problems and have a similar system to what you post (although i've got a more wimpy video card i believe) the problem does go away the longer you play as it loads things, but its still unpleasant every time a new ability or creature appears its gotta load again. If this doesn't get fixed before release it will make me pretty much not want to play the game. I'm in same boat as the OP i'm sure my computer has the balls to run the game.