All in all, I've found the Apple TV port to be pretty awesome - If you're willing to live with 720p output (It can decode 1080p, but it downscales to 720p - and it supposedly has minor lag at some points) and minor issues with seeking (which are bearable) and the current tethered jailbreak, it's a fantastic $130 XBMC device.
One thing to note is the default skin for XBMC felt laggy, but once I set it all up and switched to something else (in my case, Rapier tweaked to work on XBMC 10), it felt a lot faster and worked pretty well.
Better yet, using seas0npass and nitoTV (It's my own blog post, but http://blog.ninjahideout.com/posts/apple-tv-2g-and-xbmc-setu... details the process) it's relatively simple to set up - the caveat being it's tethered still on Firmware v4.1.1. Here's hoping the new release of GreenPois0n which will supposedly be untethered comes soon.
Seeking is slightly painful with some mkv files for me (at least over Samba - Which was expected given it's 10/100 ethernet), but in generally all the files I've tried (mostly 720p) have played back perfectly.
They won the completness category and really deserved it - the little bits of polish made it shine. It's also worth noting they actually wrote it in Sinatra during the competition, not after, a railsrumble 2009 was more a rack rumble ( but that doesn't quite have the same ring to it)
I don't know if it's on purpose, but moving around seems to always jump back to the original location (http://dl.getdropbox.com/u/25089/moving-fail.mov). And, before I could record it, I somehow got into an infinite loop jumping between two spots (fixed by clicking on the map again).
One thing to note is the default skin for XBMC felt laggy, but once I set it all up and switched to something else (in my case, Rapier tweaked to work on XBMC 10), it felt a lot faster and worked pretty well.
Better yet, using seas0npass and nitoTV (It's my own blog post, but http://blog.ninjahideout.com/posts/apple-tv-2g-and-xbmc-setu... details the process) it's relatively simple to set up - the caveat being it's tethered still on Firmware v4.1.1. Here's hoping the new release of GreenPois0n which will supposedly be untethered comes soon.