The mp is like nothing I've played. The tracker itself makes it a very immersive, Aliens-like experience, and Survivor mode has a lot of surprises in the levels. You can lock down entire buildings, weld doors, close shutters, etc... and set turrets in certain spots to really barricade yourself. Then you have claymores, proximity mines, motion detectors, and if you run around doing the objectives, you get more points and can end up winning even if the other team "survives" longer. It's not as dynamic as it should be, but it's much closer to giving me that feeling we're all looking for than any Aliens game has come.
Prime, Vakarian, and I had this poor Alien team completely neutered. XD But you can turn around almost any game with good Alien teamwork and coordination. We all proved it on Escape, where I have only seen Alien teams die and die and die. Typical, no teamwork, running right at the player, and little knowledge of how to use the Alien.
This doesn't even cover the many different attacks and abilities you can unlock for each Alien and the strategies/teamwork they create, or the weapons and gadgets you get as a marine. Throw in the customization options for fun and you've got quite an addictive little game. I just put some playing cards and grinning teeth on my helmet.
It definitely needs some balancing, but it's there for me, at least.