Within the single player campaign, the player returns as the human Chell, having been in stasis for several hundred years, while GLaDOS, a rampant artificially intelligent computer, and the rest of the Aperture Science facility has fallen into disrepair. Chell is awakened by the bumbling Wheatley, one of GLaDOS's personality cores, and inadvertently wakes GLaDOS; GLaDOS is immediately displeased at Chell's return and begins testing her again through numerous chambers as she rebuilds the dilapidated facility. With Wheatley's help, Chell attempts to escape from the facility with the use of the portal gun. Portal 2 also includes a two-player co-operative mode in which the player-characters, the robots Atlas and P-body, are part of GLaDOS' "Cooperative Testing Initiative" to seek out data discs outside of GLaDOS' range of influence, and must work together to complete each level using their own individual portal guns.

^copypasta from wikipedia

NOW

The physics of Portal have remained the same throughout the game but with many more obstacles in your path such as aerial faith plates, excursion tunnels and a variety of gels which have their own special functions. Some special functions I found pretty neat was the cross-platforming between PSN users and Steam users to play the newly introduced co-op mode. I don't particularly like the isolation of XBL users but as a PSN user I can't complain.

What are your thoughts on the game?
If you haven't bought the game, are you planning to?