I have one (or rather my son does) hooked up to a 32" lcd in HI DEF.
He swears by it and is constantly playing COD4 and 5 , Saints row etc but the controller just baffles me and i cant use it. You cant beat a KB & Mouse.
Graphics wise, your PC will piss all over it, i often laugh when he plays GTA4 or saints row at the appauling FPS slowdown, on occasion, you wouldnt get it with your pc ( but i read this is the fault of the game developers, not the console) and there is no AA.
It has some good points over pc like the LIVE format (Messenger and voice chat whilst gaming and also seeing who is online) But XFIRE sorts that for us. And the graphics on SOME games are fkin awesome in hi-def i have to say.
If you are going with the elite, then it plays blu-ray disc in hi def and comes in a bit cheaper than a blu-ray player so that would be a reason to buy, but only if you wanted a blu-ray player..... If you dont then stick with yer pc.
Get a nice 32" HD tv with the money instead and enjoy it, coz if you get a XBOX, i rekon it will be on ebay after 2 months.
Dont get me wrong, i am a massive 360 fan, but, £220 against £600+ for your pc, you guess wich is better. XBOX is nice and handy coz its cheap and in a nice little box, but, you dont need one as you already have a superior machine you are sitting at now.
Just my opinion ofcourse, if you had no pc and was after a game console then i would shout 360 at the top of ma voice, but you have a hi spec pc, so no contest :)