I thought it was good, and I'm not a big MNS fan.
It's allegorical - a bit of a criticism of fear-mongering government, and that makes it quite an intelligent film imo - compared to Signs and Lady In The Water which could have been written by 5-year olRAB, and 6th Sense which relied so heavily on audience manipulation that it didn't work for me. The only other MNS film I liked was Unbreakable, which is childish but gets away with it because the story is worked around childish things - superheroes and comic books.