The biggest updates from iOS 5 are for the iPhone and iPad, but the Apple TV also received a few improvements this afternoon.
As expected, the latest update adds AirPlay mirroring, which streams exactly what's on your iPad or iPhone's screen directly to your Apple TV. Apple's new cloud photo storage service, Photo Stream, was another addition, along with support for streaming video services from the NHL and The Wall Street Journal. (Movie trailers were also listed as an update, but we're pretty sure they've been there all along.)
While none of those services are a major addition for Apple's streaming video box, don't forget that iTunes Match is right around the corner with a "late October" release date.