So, I've been to see it.
I was very impressed. The special effects were good, and the added element of the 'dog monsters' and their toxic / viral bite increased the threat element and meant it followed the survivors into areas where they might otherwise have been safe. The 'hand-held' theme got tired after a while, since it always involves the amateur cameraman obsessively filming in situations where he would more realistically have dropped the camera (like when they were struggling from the rooftop of Beth's wrecked apartment building to the next tower), but it did make the movie feel more in your face, make you feel like you were in it, than if it was filmed conventionally.
The monster was terrific. I was expecting something Godzilla like - and I can't find Godzilla scary, I just can't - but I was pleasantly surprised. It was original and frightening, and the fact that you never find out about it, the dog monsters and what exactly their bite does to people, heightened that.
Two real gripes (well, there always are, aren't there!) - when the monster attacks the bridge, it is almost as if it sneaks up on the army and the survivors herding people across it. The last we saw it was trashing the army further into Manhattan. I struggle a bit with the idea that it managaged to sneak up on them and pounce on them from out of the river. If it had been moving on their position, someone would have radioed ahead a warning.
Gripe two - surely Beth would have bled to death by the time Rob, Hud and Lily reached her. If not by then, then surely by the time they reached the chopper and certainly well before the end of the film?
Having the attack and their attempts to escape interspersed with the partially taped over footage of their last day together - at Coney Island - before they broke up was a magic, painful, bittersweet touch.
I was very impressed and shaken by that movie. Terrific and I will be going to see it again.