http://www.engadget.com/2008/01/15/apple-tv-take-2-ipod-touch-and-iphone-yep-more-details-her/
Apple TV updates
The update adds AirTunes support for the Apple TV for streaming directly to the device.
Your average HD movie download for the ATV is going to be about 4GB -- but if you've got a reasonably fast connection it should start streaming and playing within a minute.
Standard SD movies should be a bout 1.2GB.
Just to be clear about how rentals work, they can't move OUT of the Apple TV if acquired ON the ATV. If you need to finish your movie on the go but bought from ATV, you have to rent it again on iTunes with your computer.
You've also now got "favorites," which act as pseudo-subscriptions. These aren't synced or the same as the subs in iTunes.
Front Row is NOT undergoing any UI changes (at this time). Don't expect it to look the same as the new Apple TV.
Search isn't alphabetical, it's predictive and recommendation based. So if you're looking up a letter, the results will seem out of order, but will actually be calculated to be the most likely hit based on popularity.
There's Dolby Digital 5.1, as we saw, but otherwise there are no codec changes in the ATV.