I haven't read the book. I don't think I ever want to.
I quite liked the film. I didn't think it was brilliant, or the best film ever. But I also didn't think it was bad. I guess the thing I found the most troubling about it was that I didn't connect with it emotionally at all.
I liked Ian McKellen, I liked Audrey Tautou. Paul Bettany was great and freaky (and probably one of the few characters I did connect with on any level - hah.) I agree that Tom Hanks didn't quite seem right for the role. I've always loved Tom Hanks, I do think he's a great actor, but for most of The Da Vinci Code he has one set expression and that gets annoying after a while.
The camerawork and editing were quite interesting.
It's not really a film I can talk about much. I usually find that those films haven't quite succeeded.