Looks quite ok.
I do have a few minor complaints though.
-Melee animation for marine is clunky.
-Same with alien animations. Just seems weird that the aliens seem to move on all fours almost all the time. Maybe it should be so that by pressing a key you can change the pose.
-Bolt on Pulse Rifle should only be pulled when you've emptied a mag and insert a new one.
-When you get hit by an alien the screen just appears to become red. If you get hit, IMO you should become somewhat paralyzed with motion blur etc.
-I can't see acid blood doing any damage?
Other than that I find it hard to come with any other complaints, other than that the MP footage thus far seems very bland and dull. I know that's just basic DM but still... I hope they have class system for the marines and aliens. Would be cool to be able to put up sentry guns and the like.