It was interesting to see how we can go from viewing completely alien (no pun intended) things (the prawns) and not having any sympathy whatsoever, to wishing the worst death upon our own kind so the completely alien things can accomplish their goal. I mean, who didn't feel great after that meathead marine guy got ripped to shreds by the pack of prawns?
Also, CGI was off the charts. In movies like Terminator and Transformers, it was very obvious at points that the things you were seeing were not real. In this movie, however, the aliens were top-notch, and the only time I saw a glimpse of it not being real was when Christopher was showing his son the camp they were going to on that white pamphlet. Things like that really help immersion into environments that are pretty far-fetched.