I think Rich's description of the game being a three hour game stretched out to ludicrous levels is pretty much spot on. The game is woefully full of filler, and the gameplay is pretty static. That's why they bash the game, because it's only real positive trait is the amazing work that was put into building the tense atmosphere and making the setting feel like the original movie.
I love the game. I enjoyed playing it on my first playthough. Though I haven't played it again ever since because... it was too damn long and tedious. I have, however, played the Survivor mode numerous times whenever I had a hankerin' for some good Alien gameplay.