The film does not make the error that many movies make substituting gore for horror. There is enough blood to add to the suspense, and increase the tension that is central to this kind of movie. The script is serviceable. The protagonists never engage in the typical "how could they be so stupid" stereotypes of a true horror film. Their actions, at times foolish, were consistent with their characters as urban Americans enjoying their honeymoon in an exotic land. The actions of the other characters in the film are similarly plausible.
The problem is that the movie never really comes together. You vaguely like the young couple, and that's about it. You respect the actions of the only other real player in the movie towards the end, but I doubt he even has a total of ten minutes of screen time. The monsters are scary, and appropriately monstrous. None of this is the makings of great cinema.
My wife, upon the conclusion of the movie, asked me "What's the Point?" She meant it rhetorically, because we both had no trouble understanding what was going on during the movie. Yet that comment sums up succinctly my own reaction upon watching it. It wasn't a waste of 87 minutes of my life, and since the rental was free I don't feel ripped off. It's just very sad when this had the potential to be a very good movie.