http://www.macrumors.com/2008/11/19/apple-releases-apple-tv-2-3-software-update/
Apple has released a new update for the Apple TV tonight. Apple TV owners can download the new updates from their Apple TV's by accessing the "Update Software" menu option in their Apple TV's settings.
Apple has not released any documents about the changes found, and a cursory review of the menus have shown no major changes.
Apple last released an update to the Apple TV in October which incorporated a number of new iTunes 8.0 features including the Genius playlist features.