Are you getting disappointing fps in cs:source? I know it doesn't use sli, but I can't even get 100fps stable in game with the gtx295. I used to get that with a single 8800gtx, dual 8800gtx, and a gtx280. The gtx295 works well in other games but in source I have noticed it just blows. Let me know what you get, thanks.
Are you sure you dont have VSync on?