Fun game, but the Asura engine is really buggy. Terrible physics... aliens, marines, and predators alike all jitter around on the ground when killed... sometimes they even do ridiculous backflips. Pretty bad framerate, which should never be a problem on the 360 (which is the version I'm talking about). Often the enemies will not react to your attacks as they should. Occasionally I'll claw a marine to death, and the whole time they just stand there like a statue. At times the character movement can be really jaggy... I don't know if this is the framerate, or an innate problem with the engine.
The marine dialogue is actually embarrassing. They just quack the same old lines over and over again, with occasional variations of voice type. It's like Rebellion thought they could get away with 5 marine dialogues as long as they were all spoken in a couple different voices. It really substrates from the atmosphere. With such terrible dialogue, you don't need bad AI to feel like your foes are complete idiots. "Don't relax yet marines!"... can't tell you how many times I heard that one.
The graphics on the 360 can be very disappointing at times. The Predators are not very detailed. One scene stands out in particular, where you harvest an elite Predator as an Alien. The Preds face looked so bad that I almost couldn't bare to watch. On the contrary, the alien models look pretty good, not excellent, but respectable. Marine models are so so, pretty low res textures. The environment seemed pretty graphically weak to me, though not terrible.
This game is fun, I love it, but it's chock-full of bugs that really take away from the game. I wonder how it looks and plays in DirectX11...