Not sure if this has been talked about on GZ yet, but the clever chaps at Plex have developed a way to leverage the AppleTV3 as a Plex Media Client without the need to jailbreak it (which is not possible at the present).
The approach leverages the Movie Trailer app on the AppleTV3 by redirecting the DNS entry to point to the Plex Media Server. A script on the Media Server then reformats the output from the Plex Media Server so that it conforms to the Movie Trailer app input XML format. Apparently there has been good feedback regarding the approach and it appears to be successful.
Google PlexConnect for more information.