I've got the turtlebeach X3's, which I've enjoyed. It's IR and I do get a little background noise when there is no sound playing. The up-side is that these are practically wireless--the only wire is to your controller for in game comms. If you don't need that, the wire unplugs from the headset. Very very good for MP though, the mic gives you a little feedback through the speakers so you don't end up shouting at anyone. *NO* seperate volume for chat, but I haven't had to even use the one on the dashboard, these just happen to land in the right zone for me. Not surround sound, but when you have perfect stereo directly into your ears, it's almost as good. You get a very good sense of direction since the slightest movement moves the sound very distinctly.
I'd like them to be completely over the ear like the AXT's I used to have (they were like little isolation booths on your ears, no sound in or out) but these sit on/over your ear. Very comfortable, not tight, no ear pain over time. Those X-31's look like they'd completely go over the ear, I think I would still prefer that.
I'd like to have the new X-41's, which are 7.1 surround and RF instead of IR, but that price tag is really up there right now at $173.

I believe the new X-31's are RF as well and they're only $100 at Best Buy. They have several improvements over the older X-3 models.