When I ran Vista, I actually saw performance increases in some games. GRAW jumps to mind immediately. Others ran the same, and a couple did suffer losses, on the order of 2-5fps (from 80+). Hardly anything to write home about.
“What the hell did you expect? Leave Vista under the pillow and the OS fairy would make it Win7?” -El Fiendo
“And Bring Mailman back god damnit, he is the Eric Cartman of TPU” -MRCL