After trying quite a few suggestions to fix the fps problems many people have been experiencing (GPU settings, gamebooster, fraps etc) and with none really being satisfactory, this is what finally worked for me. I now play at a constant 60fps on high settings with no noticeable slowdown.
Open the .txt file "D3Prefs" at Documents\Diablo 3
Change HardwareClass "4" to HardwareClass "1" and save.
That should be it. I saw this posted by a user named Indimix, so credit to him if he found it himself.
Hope this makes your game smoother as it did for my friends and I.
Turn off game shadows. Once I did that I had nice smooth FPS. Shadows seem to be bugged at the moment.
Turned them off....to no avail.
This morning the game was not playable and I didn't change a thing since yesterday evening!
Then I removed the battle.net folder and, once a new one was created, the game run decently.
Still I keep having stuttering and microfreezing.
I set everything to minimum, everything to maximum and everything in between: game quality does change, game performance does not change.