I played it quite a bit yesterday. It's fun alien smashing time. Played a few rounds with different friends and several with pubs.
Biggest problem is it's a coop game, with no in game VOIP. 2nd biggest con is it's limited to 3 people.
There's 4 campaigns with between 3 missions per campaign, so overall it's fairly short. Seems to take most people 6-8 hours. There is also some horde modes I didn't get a chance to play yet. On the other hand, it's not a full 60-70 bucks that most games come out as.
5 classes (gunner, demolisher, technician, doc and recon) lots of weapons, and several consumables. Each class has 1 passive and 2 active abilities and they're all useful in their own way.
I don't remember how many difficulty levels there are, but it's something like 6.
I'm not a huge fan of it being 3rd person.
I'd say it's fun and go for it. It nails the aesthetic of the Aliens movie. The problem with a coop game like this and waiting a year or two to pick it up on sale is people may or may not still be playing it by then and if they're not, you missed out.
Disclaimer: I'm a sucker for coop games and the Aliens franchise.