No, but it makes a nice all-round media machine, I modded mine for VGA so I could play all the games in 480p and it is sweet.
XBMC is so very there, the only thing it can't do is HD, I just look at the 360 and salivate ($300 eh??), plus it is VGA out-of-the box (well, at least it is officially supported with the cable).
AND YES, it is just a computer, but one with only 2-3 moving parts and that only costs around $70-80 right now.
I used an action replay memcard and the splinter cell exploit. So I didn't
Have to open it, but then I put an 80GB HDD (shoulda been a 160GB, but it wasn't lockable), and then modded an LG 16x DVD drive completely stealthed with the cover, looks stock
h34r: .
I rip DVDs straight to the HDD and then play them with XBMC (full DVD menus too).
I have a PSP, the Xbox blows its doors off as a multi-media device, solely because of the XBMC (well that and the 64MB of RAM and the Geforce3, and the P!!!).
Although I couldn't give a crap about "topmenus" I don't need to pimp my crap, it is cool because it is functional, I have 3.30OE-A on my PSP, AFAIK it doesn't have the topmenu support, but at least Daedalus has my 120 Star save mario game so I can blast around the Castle with my wings
PS, you can also Hack games ripped to the HDD, run straight Divx movies, and play Youtube (yep, just plug it into your router). Also it is much easier than a PC to take to a friend's house loaded with 100 to 200 GB's of Anime and games.
Oh, and last but surely not least, the PSP has no Keyboard support, my USB keyboard makes it a breeze to find Youtube videos.
Personally I don't like the way M$ is trying to "integrate" the PC into the 360, I won't buy it if I can't play
ALL my media off the internal HDD and it gets bigger than 20GB (80-200GB is about the range that makes sense to me, of course if I could hack it to a 500GB $120 drive that would be cool).
I don't need a PC on with the 360, it kind of makes it redundant.