I saw the movie this weekend and I'm conflicted.
On the plus side: Marcia Gay Harden as Mrs Carmody was truly frightening - I celebrated when Ollie Weeks shot her. Speaking of whom, the actor who played Ollie did a brilliant job. He brought the character to life and I really cared about what happened to him. The child actor who played David Drayton's son also did a good job - those scenes where he sobs almost hysterically were heartbreaking.
On the minus side: I didn't enjoy watching Thomas Jane. I think his acting is wooden - he's a poor man's Christopher Lambert (and I don't think Lambert is a brilliant actor either). I couldn't muster much sympathy for the character as a result. Also, the ending differed markedly from the book and, while I can see how it made cinematic sense, I found it a little too pat when I thought about it afterwards. They couldn't have waited five minutes?