Just a head’s up. If you are a big Portal 2 fan that you can now download the new and free, Peer Review dlc for the game on Xbox LIVE.
Peer Review is the first DLC for Portal 2 and features a new co-op track that continues the story of Atlas, Peabody and GLaDOS. The DLC also includes both single and multiplayer challenge modes, plus leaderboards so you can compare your portal placement and time scores with the Portal community.
You can add the DLC to your queue here.