Apple is rolling out a fairly minor update to its second and third generation Apple TV units this week. Version 5.0.1 brings HD previews for iTunes content, AirPlay fixes to help certain iOS apps connect properly, Home Sharing improvements, a Netflix login and navigation patch, and the usual stability and performance enhancements.
The update is available immediately and can be obtained from the update software option in the settings menu of Apple TV. If you're an aTV Flash user then it's probably wise to hold off on the install until an update is issued by FireCore.