I can see a difference, but it's not much, it can be very beneficial for fast paced games.
There are a lot of 30fps games out there that are smooth as butter though. I can tell more of a difference between an inconsistent 25-30 fps and 30fps rather than 30fps and 60fps.
For example I can see more of a difference between Crysis 2 and Final Fantasy XIII's framerate rather than Final Fantasy XIII and Modern Warfare 2's framerate.








