I've noticed that observable lag in framerates seems to be the direct result of having an on screen FPS counter. Honestly. I seem to enjoy a game far more, even if it is running under 60fps, if I don't know FOR SURE that it's doing so. Try it. Turn of FRAPS or whatever other FPS counter you use and play for awhile. The fps are still the same, but not actually seeing it dip and spike can do wonders for your gameplay experience.