Short 'n Fun
Well, if you were looking for a game that just give you a gun and say " kill the xenos " you'r now looking in the right place guys ! Most modern FPS have many " cutscenes, walking around, exploring landscape & collecting objects " that, frankly, sometimes just discourage to play another run, meanwhile, the short premises give this game a good replaybiity over a 2 hours long campaign.
If you liked the movie, you'll be glad that they didn't add fan-created enemies to make it last longer (do you remember how bad were the " new bugs " in that old StarshipTroopers game ?) : there are just the mobile turrets, the troopers and the ships.
I never saw it going down in price, so, i'd suggest to buy it for 9.99euro. It's better than spending 59.99 on COD (the gameplay is more or less the same, autoregen ecc.)