Saw it last night and really liked it. The g/f went with me and liked it too. She did comment that it would appeal to men more than women. I'd like to think that was because they didn't tack on some B.S. love story that stuck out of the movie like a 6th finger.
The parts that gripped me were the more documentary portions. For instance when... aw crap..hold on...
SPOILER ALERT - SPOILER ALERT - SPOILER ALERT
The parts I felt more about were when he was showing how a normal guy, someone doing his job, could be wrangled into killing the alien infants. In the beginning when he calls in a "population control" unit on the shack with eggs/pods in it. "They go off like popcorn! See!" The documented genocide reminded me of various photos and video's I've seen of that. Normal guys, doing a job. Not realizing it's horrific.
Then, the contrast with when they had the hero strapped down and firing the weapons. Well, he wasn't really firing them as they were using a cattle prod on his arm even when he volunteered to shoot. Then, the final shot when they walked an alien out with an X on it's back. It was obviously scared and unsure. All that over the patient's unanswered questions, pleas for mercy, etc.
Strong.