I saw this film the other day, and I actually really liked it. It was exactly what I expected (maybe a little better). If you want to watch a really well thought out film with lots of character development and interesting subplots this is not the film for you. If you want to watch a bunch of U.S. Marines beat the tar out of invading spacefreaks, then this is the film for you. From when we first encounter the aliens to sometime in the middle, the movie is a nonstop thrill ride. Stuff explodes, aliens get splattered, humans get burned by lasers. In case you didn't already suspect, this film is very violent. Although there isn't a lot of blood, there are certainly a lot of deaths. The action is unpredictable and zany. One minute everyone will be walking somewhere between point A and B, the next, they're crouching behind burned out cars and houses as aliens pour ungodly hellfire onto them from above. The special effects were also quite good, with the exception of a couple bad animations here and there. That being said, the movie suffers when it slows down. The dialogue is poorly written, and delivered decently, but not well. Aaron Eckhart however did a wonderful job as a stony faced marine staff sergeant who keeps a cool head when under fire. Most of the storyline is pretty standard war movie/alien invasion stuff. You know, when after a bunch of fighting everyone gets discouraged and then the leader gives a big motivational speech and the inspirational music plays and everyone feels heroic.
So don't expect a masterpiece of modern cinema, expect alien guts and lots of shooting and I guarantee you will not be disappointed.