Apple today updated Apple TV (along with iOS). Apple TV firmware is now version 5.2.1.
The latest update includes some bug fixes and an update to the Hulu app that gives it a complete redesign. To update, simply turn on your Apple TV, go to Settings>General>Update Software. Apple TV will search for an update. Hit Download and Install. Apple TV will do the rest.
After that, you will have the latest firmware for Apple’s set-top box.