Well usually the higher the better. But just take it as high as you want to, I've heard that some people don't like anything higher than for example 75hz.
But I love my 100hz
Yeah, I do find past 75hz, my eyes started to blur when I had my old monitor. Don't know if its the monitor or what, since this one I have now only goes to 75hz.
Though if it was the monitor and it could reach 100hz for example, if a game was going at 100fps, and you had V Sync off, you wouldn't get any of that flickering!
The higher the better untill you get to the stage where your monitor can't handel it and it goes fuzzy. 100hz is probably the standard and anything over 130 gets fuzzy