I game fairly casually—I might boot up the Xbox once a week for 30 minutes or an hour at most. I used to prefer gaming with a keyboard and mouse on my previous desktop PC but I never had enough desk space to keep it always connected so it was a bit of a cable juggling to connect it so I never used it that much.
Eventually I decided to get an Xbox (quite a while after it launched) and it's been perfect. I tend to play car racing and FPS games; for the latter not having a keyboard and mouse was annoying at first but I got used to it.