XBMC, the best-loved open source media platform for TV, is now ported to AppleTV2 and iOS devices. This makes AppleTV2 the cheapest full featured brand name media streamer you can get. This must worry other media streamer makers such as Roku and Popcorn Hour, as you can get the best of iTunes world and best of media player in one box.
XBMC completes the AppleTV2 as a media streamer and player. With XBMC, you can now view media outside of iTunes, with codec not supported by AppleTV2 such as divx and MKV. And XBMC will transcode 1080p media to play on AppleTV2. XBMC is installed as an app within AppleTV, which means you can keep using stock player for your iTunes content and rental. All these in one of the best user interface for a media platform on your TV.
One caveat is you need to jailbreak your device in order to run XBMC on your AppleTV2, iPad or iPhone 4. But it is better than nothing.