Prior to 6.0.1, Apple released a major update in September that added iTunes Radio and AirPlay over iCloud as the big offerings. This time around 6.0.1 adds the new iMovie Theater with the new video sharing technology that Apple showed as a part of the new iMovie for iOS and Mac at the press conference.
From what we can tell there are no other major additions beyond some backend fixes and additional performance gains. AppleTV owners should be able to download it now.
Rumors continue to suggest that Apple is working on something more for AppleTV, but that may not come till the rumored TV with built-in AppleTV functionality arrives at some point in the future.