Aren't you forgetting the response time?
How is it better for gaming, unless you're meaning 3D gaming?
Well, actually, what I meant was: most 120Hz monitors have WAAAY better response times than normal panels, which make them far more suitable for gaming (I don't believe any manufacturers claimed response times, because they are thumbsucked most of the time). Fact is, you need to have a very good reponse time for 3d to work at all with alternate frame method. Oh, and yes, the monitor will allow you to set the refresh rate to 120Hz, so you also have the vsync cap raised from 60FPS to 120FPS.