Too many characters
I think the main problem this movie had was an abundance of characters that you didn't care for. They should have scrapped the teenagers and the random townspeople they met in town so we didn't have to endure the stupidity of them taking matters into their own hands.
I actually found the movie to be good in terms of the Alien/Predator scenes(even though Would being the only predator was stupid) along with the idea of town being in a blackout.