Yeh Im using win7 x64 with the vista x64 9.1 drivers.
I didnt get a benchmark before I installed, I forgot, but as I said Ive noticed GTA IV is running a lot smother. Havent noticed much in my other games, havent tried Far Cry 2 yet though. For me it deffeniatity hasnt made my games run worse. I never tried those beta drivers so I cant compare to them.