Lets take a break from tornadoes...
I loved the movie, it far exceeded my expectations. The showing was sold out and it received applause when the lights came up. I've read the book.
That said, Kathleen (who has not read the book) thought it was only "OK" (not "bad").
I've read some critics (i.e., Roger Ebert) hate the movie. I believe this is more due to his personal politics than an objective review. As evidence, take a look at the rave reviews at IMDB. The book is 1000+ pages and was a difficult project (as evidenced by the multiple attempts in the 40+ years since the book was published) to bring to the screen. They succeeded.
Go see it for yourself! I can hardly wait for Part II.