I loved this movie. A lot of people complained about the camera shake, but I actually thought that it added to the film's fiction, making it more realistic and actually plausible. You don't hear that about a lot of monster films. There IS a lot of innuendo in the beginning but I think that's a non-issue due to the fact that most 13 year olds have heard all that by then. There is quite a bit of gore in this movie, a bit too much for PG-13. The S-word is dropped a lot, too, but like I said about the innuendo, it's a non-issue. The gore is mostly in one scene inside a makeshift military hospital, where you see a corpse with the chest exploded being pushed on a cart. Later in the same scene, a character begins bleeding from their eyes and mouth, gets pushed behind a curtain, and promptly explodes, splattering blood all over the curtain. I wouldn't recommend taking anyone less than 15 to see this due to the gore and fright factor, but I still thought it was a very good movie.