But wait, what is all this "Peer Review" stuff anyway? It's a shiny new bit of DLC for Portal 2, which Valve has been working on and is now all ready to show off. The pack will be released in all regions on all platforms (Steam, Xbox Live and PSN), and yes - there's even a Mac version.
Peer Review is designed as an extension of the game's co-op mode, continuing the story of Atlas and P-Body. This time, you have an all new, mysterious co-op test track which sees you facing off against GLaDOS once again.
There is also additional single-player content, plus co-op Challenge Mode - and leaderboards have been thrown in, so you can compare Challenge Mode scores with friends and the community at large.
Worth waiting for, we think - although you won't be waiting long. Grab the Music to Test By soundtracks, plug in your headphones, and count down the hours until Peer Review is released for Portal 2 on October 4th.