It's not just the second-gen Apple TV getting a shot of XBMC today; as long as your iPad is jailbroken you can now load the media center on the iOS slate, too. As with the Apple TV install, this is the full version of XBMC rather than just a remote app, supports hardware video acceleration, and the same software will even work on the iPhone 4.
Video demo after the cut
The experience on the iOS smartphone is, XBMC admits, "currently frustrating" which seems to imply they're working on a better version. Still, it's an example of how capable the Apple A4 processor - found in the Apple TV, iPad and iPhone 4 - is.
Full instructions here.