Borderlands 2: Interesting new enemies, some real variety in the abilities and AI. Didn't get a multiplayer game, unfortunately, but still a good idea of the gameplay at least.
Aliens - Colonial Marines: Amazing. Simply, utterly, awesome. Multiplayer game vs. playtesters (Marines vs. aliens) was immense fun. Various kits to choose from as a marine (I only chose from standard pulse rifle/pistol, and shotgun/pistol, but you can also pick up a smart gun as a "powerup", similar to how aliens can evolve to a very large "bull" form.) Looks great, and the Aliens can really take advantage of shadows, ducts, and the environment.
Far Cry 3: Very nice to look at, but not much sensational about the game. Certainly no noteworthy gameplay elements that I came across.
Strike Suit Zero: (Gundam-style space shooter) Gorgeous graphics, little else to it. Suit mode not really effective in space, and that's the only area we got to play. Very repetitive gameplay, it seems.
DayZ (1.7.2): Zombies are more alert, now. That's about it (Test machines kept crashing most of the day)