I play mostly, TF2(works perfect even with max), L4D2, and Currently City of Heroes(many settings have to be lowered).
Of the games I tested the problem definitely arose with slightly newer games such as FEAR 2, Borderlands, and most notably Dead Space(which showed the most of this response lag). It also comes up with CoH when I put the settings higher.
There is no fps loss however, which leads me to think it might not be a graphics issue. It's just that using the keyboard/mouse with settings high yields a noticeable delay from button press to actual movement on-screen.