Finally gave this game a go last night. Played 2 games as the marine, my buddy playing the Aliens. You know what, it was a surprisingly well put together game that did require some well made plays and thinking. I'm quite eager to play some more actually and build my own deck (used the recommended decklist in the rulebook). I do feel that you might need 2 lots of the box to really make sure of it though.
I think you're going to be building around the main characters and to do that effectively you need more of certain things (like the Queen wants a deck made of lots of swarm characters that are all the same character name, the Alien Ripley wants just about all Locations that give Humanity, etc).