We didn't see much. It looks like the new Left 4 Dead will take place in New Orleans, or a city very much like it. The four survivors were all new, and fighting off zombies with chainsaws, among other weapons.
Jordan will be stopping by Valve's booth later in the week, so I'm sure he'll have much more to tell you then!
UPDATE: Valve has issued a press release offering a few more details about Left 4 Dead 2, promising an even deeper cooperative zombie apocalypse thanks to the AI Director 2.0, an updated version of the AI Director found in the original game. The new version will provide even more immersive and dynamic gameplay with the ability to procedurally change weather effects, world objects and pathways, and customize enemies, effects and sounds.
"A large part of how Left 4 Dead became 2008's top-selling new IP on Xbox 360 and the PC was the custom-tailored gameplay made possible by the AI Director," said Valve President Gabe Newell. "With the knowledge gained from creating the original, new technology, and a passionate team, L4D2 will set a new benchmark for cooperative action games."
The game will be "much larger" than Left 4 Dead, with more co-op and Versus campaigns as well as Survival mode maps available when the game releases. Left 4 Dead 2 is currently slated for release on November 17 for the PC and Xbox 360.