I just bought a used 360.
A friend of mine has a PS3 which I borrowed now and then to play some PSN games (not really into all these 3D FPSs and 3rd person action games that seem to be 99% of all games released) and I never got excited enough to buy one myself. I played some Castle Crashers a while a ago though and was excited about the 360 since then!
All I can say is that I think the 360 is really worth getting just for XBox Live Arcade. You get one or two demos A WEEK FOR FREE.
For me thats the perfect deal since I don't have time to spend 40+ hrs on a killzone or halo or what ever!
If you're not really interested in PSN or Arcade games I guess it's only worth it if you REALLY want Halo and Gears over Killzone.