It's my personal opinion (shared by many) that Hayao Miyazaki can do no evil. That, and adding the fact that they cast the lovely Christian Bale in this movie, I am of the opinion that this movie rocked! (Especially being that I saw it after such an attrocious movie like War of the Worlds)
I've never read the book (by Diana Wynne Jones), but the movie was great. It was very imaginative, and dare I say it, romantic. From the very beginning I was sucked into this world they created, and the characters (one voiced by Billy Crystal) kept me wanting to watch more.
Really there's nothing bad to say about this movie. You might not like it if you don't like anime all that much, though I think anyone could enjoy this for what it is.
And hey, Jean Simmons was in the english version (no, not the singer from Kiss, but the chick who played Ophelia opposite Lawrence Olivier)!