My $.02
I've been using Ubuntu on my desktop machine for almost 2 months, and I love it. Gnome is great, although I haven't got the experience to compare it to the other options.
I'll never go back to windows. I still have to boot windows for some of my games, which I'll have to live with as a PC gamer. But the games that are linux native run great.
I've got Quake IV and NWN, along with a lot of free/open games. I'll be picking up Enemy Territory: Quake Wars and Unreal 3 when they come out this year, since both are confirmed for linux.
I also have BFX 2006.2 running on an old Compaq PII 366mhz laptop that my wife uses for school, and she loves it. It's really given the laptop a new lease on life. It was unbearably slow running win98.