TiVO Premiere, Samsung Blu-ray, and my 13" MBA which uses Plex (the media lives on a 2TB Seagate that is plugged in to the MBA when in use).
Other than the new MBA not having an IR receiver, the MBA/Seage work well for Plex. I set up both my wife and my maxed-out MBAs with Plex and directed the media server to look for the Seagate 2TB drive. While it means that you're not totally synced on watched/unwatched, it means that whomever is home can just plug, run Plex and watch whatever they want.
That set up will work until the ATV supports local storage through the USB.