I chose "Let application decide"
saw no difference. Also tinkered with Use Advanced Settings, same results. Don't know if this problem is only for COD games.
Bad Company 2 plays fine with Frames over 100 on highest settings. Tried V-Sync, very bad input lag.
Left 4 Dead, runs great, doesn't seem to have the same problems of COD with jerky frames, but when I choose V-sync, the same problem, input lag. Triple Buffering makes it unplayable.