To be honest I was definitely disappointed after viewing the film, things were changed, a lot was left out, the whole film seemed rushed. Personally I would like to know if the director actually read the entire book before writing the script for the film...
It seems to me the film was only set to represent the interesting parts of the book, and parts that would make the film a hit in the cinemas and on DVD release. It felt like there was a complete lack of a good background to the film, which you certainly got from the book.
However, I'm glad I watched the film. Its made me appreciate even more what you can get out of a book that you cannot get from a film. This isn't me saying I wont watch the film version of a book ever again, because I will. I think its a good thing to do, as it makes you realise even more how good the original book was.