I tried one at the Apple store today and it's pretty cool. The scroll wheel seemed very sensitive, but I think you can probably adjust that. There's literally no physical indication of any buttons, and right clicking only works if you use your middle finger. The reason I quit using the original Apple mouse was because it didn't work well for first-person shooters; the Mighty Mouse is similarly handicapped for FPS gaming.
I'll stick with my Logitech dual-optical.