From what I've seen, and in my opinion, the game looks worlds better than the last demo we saw.
A couple things that I don't like. The sounds, like others have mentioned, aren't spot on. They need to be, no excuses. The pulse rifle sounds bizarre. I see what they're trying to do with the pitch changing... but it's not sounding right.
I can't quite hear the smart gun... I want to say it sort of sounds like the movie, but I'm not sure. It NEEDS to sound like the movie. I don't know why so many versions of this gun have a completely innaccurate sound, but I'll be very disappointed if ACM doesn't nail it. Also, i don't think it should allow you to see through walls, but consider this - when Drake/Vasquez are using the smart gun, they have one eye closed. I'm assuming this is so they can see what the gun is picking up. Perhaps that should be integrated into the game. You can toggle having one eye closed (via alt fire) and what you see on screen would reflect this.
The alien blood looks much better (in campaign, NOT in MP) but seems to dissipate in the air? Why? When aliens are killed they make a mess! Hopefully this is adjusted.
Main, and biggest gripe... the motion tracker. Red dots? No... just no. They weren't red in the movie, they shouldn't be red here. Also, they shouldn't even be dots! In the movie, the object being picked up almost appears cell-like on the tracker. As there are more objects picked up, these cell-like objects begin to connect forming a mass. Why hasn't a single aliens game reflected this? I was fine with this back when the original AVP came out, but that was 1999. It's been 13 years, fix the tracker please. Also please make the tracker audible whether the marine is holding it up or not.
Lastly, I'd be willing to bet GB is reading these forums for feedback (the sail tail is gone, isn't it?) so I think it's great we keep the constructive criticism coming, but let's try not to be too negative. These guys are clearly excited about the project and working really hard. When the final product comes out, it's not going to be Aliens. Nothing is ever going to be Aliens except Aliens and our expectations should take this fact into consideration. I thought about it, and with this much build up, there's a HUGE chance I'll initially be disappointed with ACM which is why I'm going to spend some solid game time with it before I offer an opinion.