Update: Apple has now posted the support document listing the changes and it looks like they are a couple small bug fixes that come with this update. Here they are:
* TV resolution fix: Addresses an issue that causes some high-definition TVs to incorrectly display at 480p.
* Download fix: Addresses an issue that may cause a movie or TV show to be re-downloaded.
Apple has just launched iOS 4.2.1 for the Apple TV! Now, there is no word on what exactly this new version does, I have updated to it and I don’t see any visual or feature changes yet, it downloaded in seconds to my Apple TV.
Apparently iOS no longer has to download the entire ipsw, Apple finally integrated the ‘quick-patch’ system, hopefully we’ll see this in iOS 5.
The Apple TV reports it as iOS 4.1.1 (which we all know is really iOS 4.2.1), more updates as to what the update brings as we get the info!