I thought headsets were retarded and just got tired of replacing the pos Microsoft one you get with the Xbox. I bought a set of X12's a few months back and they're great. It won't necessarily make you play any better but it does make the gameing experience more enjoyable.
I didn't ever think a headset would be worth that much money to me, but decided to get some X12's anyway. Best spend ever. The sound is amazing, it really helps to immerse yourself in the game, even others besides CoD.
I'd say they're well worth it, and the one the Xbox comes with is complete garbage. Just don't expect to sound ***** in this game since footsteps suck.