Its a good TV tuner from what I've read (I have the Asus which is also excellent.) The video in is acceptable for consoles, but is by no means excellent. Definitely use S-Video as the difference from composite (RCA) is pretty dramatic. Ideally, a VGA adapter directly to your console would be the way to go, but there is no adapter for XBox that takes advantage of its HDTV display capabilities. Its gonna take awhile to get used to it, as your monitor displays much higher resolutions than NTSC, so it doesn't look nearly as good as on a TV. A VIVO videocard might also be better, as TV Tuner cards use video overlay through your video card to display images.
Chiz