It is useless to draw frames more often then your monitor can refresh. That means that FPS greater than your refresh rate are generally useless... the one exception is when you end up with a better physics simulation if you can go through more iterations of your game loop. E.g. colliding objects don't penetrate as far, step size decreases which makes a difference for some algorithms...
Even then, you should not actually update the screen faster than the monitor refresh... since physically you can't it is a wasted operation.
hmm seems a lot of guys are new in the game business, ok ill explain what i mean.
U cant get a FPS greater than monitor refresh ( impossible in fullscreen ), maybe windowed mode needs a little tweak, but i speak about realtime games. ( for e.g. UO is a good example )
I am drawing 100 terrain tiles, around 500 additional images and all this rendering is done in about 5ms, now the VSync kicks in and waits for you.
Demos like 2ndReality have a render / game physics loop which has NO SLEEP AND NO SECONDARY THREADS ITS DONE IN ONE THREAD.