Watched this one on dvd last night. I was pleasantly surprised by it. I remember not being hugely impressed by the book - it wasn't bad or anything, just not especially good either.
However, the film brings it all to life very well. The magical kingdom is just as magical as you might desire, and the acting is generally good (often over the top)... I did think that Ricky Gervais and Robert de Niro's pieces didn't quite work, however.
The special effects for some big pieces of magic were very well done, and there's about the right level of humour to contrast with the nastiness of the evil witch and princes who are involved.
Recommendation: If you like fantasy/fairy tale films, see it.