Been playing this game obsessively since it was released. In both Xp and Vista..
Updated to the RC1 Service Pack for Vista, and using the 169.25's, with SLI
frame rates are playable, but I still think it needs the patch before I will
consider it fully 'working'. (Works for some people, doesn't work for others)
In Xp it's just ridiculously smooth, I'm sure the average FPS rarely goes under
30.. this is running 1280x1024 with 4xAA and everything maxed using the Dx10
So for now, Xp is the way to go.
EDIT: Yup, just downloaded Fraps and tested in XP. Average 35, never dipped below even with lots of action
on the screen. FPS went between 35 and 50+. Not to shabby.