Valve has made their E3 debut appearance, giving us the wildly brilliant official trailer for Portal 2, complete with a familiar voice, turret buddies, some interesting game modifications, and a lot to look forward to when Portal 2 unleashes co-op shooter-puzzle action on us. Having Valve appear during the Sony press conference also implies that the once-Xbox 360 and PC exclusive title will be appearing for PS3 owners as well.
"I think we can set aside our differences for science, you monster."
The release date for Portal 2 has also been pushed back to 2011, but Valve assures us that it's worth the wait. From the look of it so far, they're probably right. Edit: It looks like all of the videos were removed except the one for IGN - here's the Portal 2 trailer courtesy of IGN.