And running the game in 100+ fps compared to 60-70 actually does a difference even if you might not be able to see it, as the mouse & keyboard input is sampled at a that higher rate you can get better control and a more smooth experience.
But for a _really_ smooth experience at high FPS; try the new 120hz monitors for example the stereo-compatible ones from Samsung. Have one on my desk and it is awesome when hitting 100+ FPS."