I actually really enjoyed this movie because it's not a traditional horror movie by any means. And the acting wasn't as bad as you're making it out to be, it had it's moments though I admit, but it wasn't terrible. I mean, since when are horror movies known for excellent acting anyway? lol People don't go to horror movies to see Oscar winning performances.
The thing about this movie is that the focus isn't on the monsters and monsters attacking/eating people, the focus of the movie is on the characters themselves. It's very much a psychological study of what humans do and how they react in life threatening situations when the rule of law no longer applies.
The dynamics that erupted in the grocery store between the characters was pretty interesting. They did an extremely great job of making everyone in the store wary of the jesus freak at first in the begining of the film, but as more people died, and the more scared people became, the more people turned to the jesus freak for answers and comfort, and they eventually became a scared, angry, murderous mob.
And eventually it was your fellow man that you had to watch out for and be afraid of, and not the monsters anymore. By the end of the movie taking your chances out in the Mist with the unknown was better than staying with the angry murderous mob.
It's really great. I definately recommend it. But this is the type of movie you'll either really enjoy, or really dislike. So you have to make up your own mind really. lol