Great premise, direction, and gore effects. The effects really are amazing, and pretty much the sole reason I'm giving it an extra star. I really wanted to like this movie. I was fully in for the first third or so, the premise is really cool. The writing is pretty bad though, in my opinion. To a frustrating extent. Seems like they had the movie storyboarded out and in order to hit those points they just made every character make dumb, unbelievable decisions. I've read some people say that it's intentional; that the main character is supposed to be dumb, but nearly every single character in the movie makes poor decisions that only serve to further the plot. From cops that are only in one scene to the exposition dumping characters that are introduced in the second half and everyone in between.
So many completely unnecessary threads get brought up but never resolved. And finally there's a scene halfway through where the main character says "we need to talk" about a dozen times without ever actually saying what he needs to. Thats just dog water.