After canceling their big Monday night Portal 2 event, Valve settled on a understated little affair in a quiet office on the second floor of the Staples Center. Project lead Eric Johnson took us through a canned video presentation with some commentary on his part of a bit of Q&A afterward. I'm not sure what I can tell you about Portal 2 without without coming across like a drooling idiot. It's amazing. There's a clearly stated focus on augmenting and improving on all the elements of the original that stuck with fans and it really shows.
Best example of this to me was the weird fascination people had with the weighted companion cube in the first game. Something Valve is doing to build on that fascination is provide a new companion that you carry in the world like the cube -- but it's a personality core. It speaks to you as you carry it much like GladOs would, only it speaks in a charming accent and had some incredible funny dialogue in the demo. Fun fact: the voice is done by Richard Lord, an artist who works for Valve. He's great.
There's a great many other new addons to the game including full coop levels that are separate from the main single player story and a handful of new portal gun powers. It's worth not looking too deeply into these new abilities and the puzzle ramifications they bring if you can manage it. Portal is all about discovery and the sequel is no exception. You're already going to buy it anyways, so just rest assured that they're setup to knock it out of the park.
PC/Mac/PS3/Xbox 360 all released on the same day sometime in 2011.