Apple has just released Apple TV software update 5.1.1 (build number 10A831) for 2nd and 3rd generation Apple TV.
Here’s what’s new in Apple TV Software Update 5.1.1 according to the release notes:
iTunes Up Next - Adds support for Up Next with iTunes 11 or iTunes Match. See upcoming songs when playing music on your Apple TV. Add new songs and edit what’s queued with your Remote or with the Remote app.
Stability and performance - Includes performance and stability improvements with the iTunes Store, AirPlay, Netflix, iTunes Match, and wired Ethernet connections.
Jailbreakers should avoid upgrading to Apple TV Software update 5.1.1.
If you don’t care about jailbreaking then you can install the update directly on the Apple TV via the Settings menu.