So far I'm really enjoying the game, I'll start off with that.
I'll also try to make this as spoiler free as possible.
The Good
Accuracy: The look of the marines is spot on, as are most of the weapons and the weapon sounds.
O'Neil: I love this guy. Who ever did his voice acting did a great job IMO
The single player is pretty engaging, its not up there with Halo or GoW engaging but I think its a step above COD and the like.
The graphics on the character models and most of the environments are pretty good, the character movements seem pretty fluid as well. Not to many hiccups, though there are some.
Aliens: They do act like the Aliens in the film, they hurl them selves at you and the marines. Some people said this was bad and made them stupid, but its pretty film accurate, albeit there's no power for them to cut.
Legendary weapons: I've enjoyed the ones I've found so far, although at least one of them should be nonexistent. The idea is cool.
Allies: You almost always have a buddy. I hate games that make you lone wolf it out, it was the main thing I didn't really like about AVP2010. I like me some allies.
The Bad
Wey-Yu mercs. It wasn't nessesary for them to be on more then one or two levels imo. Its an Aliens game, I want to kill Aliens.
A better graphics engine would have been nice. I'm spoiled by things like Halo 4 and Bf3, and I know I said the graphics weren't as bad as everyone says, but there's always room for improvement.
Not enough allied bots: I like cannon fodder bots, the game that had these kind of bots the best was the Halo series (1- reach). There's no emotional connection to them, yet you kind of start to form that. I like when my allies follow me and theres the risk of them dying. This game could have benefited from Halo style allies.
Atmosphere: it was almost there, just a smidgeon away from being complete, but there wasn't any real sense of urgency in the game, I want to feel like I could die at any moment.
Vent/Floor pull throughs: What happened to this? I was so excited for this it wasn't even funny.
THE BIGGEST LET DOWN'S (for me)
The Crusher: He seemed so small compared to the E3 demo. It was like fighting a bull dog to be completely honest. The Raven was for more intimidating, the Crusher was just very, VERY puny and lack luster. It was one of the most pathetic things to fight in terms of a boss, the only thing I thought was worse than this was the Prophet of Regret in Halo 2.
Hudson's Pulse Rifle: The thing is burst fire. I don't mean good burst fire like BC2 or BF3, I mean the burst fire that takes 2 or 3 bursts to kill something on recruit and hurts your finger in the process. I love the look of this rifle of the default one, even down to the iron sights, but the burst fire really pisses me off because it's something gearbox had to go out of their way to mess up. Ripley's pulse rifle is full auto, further making it a big middle finger that Hudson's isn't.
For an average gamer who doesn't really care about the franchise I'd give this game a 5/10 maybe a 6 if you really like sci fi shooters.
For a fan of the franchise I'd give it a 7/10, or an 8 if graphics aren't a big deal for you. It wasn't really for me, they where good where it counted.