In my case, the biggest boost I got in crysis under vista 64bit was buy upgrading from 2gb to 4gb of ram. Upgrade was done after the patch came. Patch gave me 5 to 10 FPS & less slowdowns but the ram gave me 10 to 15 FPS. (the patch helped probably make better use of the extra mem)
I'll try readyboost on top of that (hope my drive is compatible to see if I can squeeze more fps.