So yeah, as you've probably heard this level is not in the game, and having finished the single player campaign, I can confirm it:
http://www.youtube.com/watch?v=NZHA58-_2Eg#wsSpecifically made to make the game look good. None of this happens at all in the game- doesn't look like this or play like this. This "demo" was purposely manufactured on a PC to sell it all.
This is clearly false advertising- incredible false advertising. Reminds me of the Predators trailer where they had all those lasers on Adrien Brody, only for that not to happen in the film, and Robert Rodriguez said they only showed that to pretty much sell the movie.
I also love how at 4:57 of the video, Randy says "Aliens can climb on the ceilings and the walls..it's all driven by sophisticated artificial intelligence". LOL.
This is really bottom-of-the-barrel- marketing from Gearbox. I didn't expect them to go this low.