I love alien invasion concepts, but this was a let down. I won't spoil anything with details.
First complaint was no real story; just run and gun action and much of that behind a documentary style jerky camera. There was a brief introduction to the characters, but not enough to make you care about them. All of the characters were stereo-typed too heavily and pretty much borrowed from other movies. There was an attempt to shoehorn dialog in between the action, but much of that was hokey and cheesy. I think a decent story and some more character development would have made it a better experience. After the first 20 minutes, boredom set in, my friend fell asleep and I spent most of the time counting the war movie tropes.
I liked many of the visual effects, the aliens were not as horrible as they were described to me. The gun battles were well executed from what I know of them, but it was too difficult to tell the characters apart in many scenes.
As for the theater experience, there was not much there either. There was nothing that made me think, "I am glad I saw this on the big screen." I don't think there was any swearing and almost no gore. Unless you really need to see it in a theater, rent it on DVD in a month or two.
The cynic in me says it was the longest commercial for the US Marines I have seen, all it needed was the toll free number. I see it as the product of a mating of 'Independence Day' and 'Black Hawk Down' delivered by someone who learned child birth from a video game.
I know I sound negative and I won't think ill of anyone for enjoying the movie, I am just disappointed in it.