I am bumping this because I just got back from seeing this movie, and it was brilliant.
If anyone is put off by the usual pace and style of Wes Anderson, you can expect different from The Fantastic Mr. Fox. This is a kids film, so the humour in it is far more accessible and the gags are far more obvious. The dialogue, however, maintains the subtle wit that Wes Anderson successfully, albeit formulaically (not a real word, I know) utilizes in his films. There's a good chance Noah Baumbach had a little more influence at the writing table. In terms of keeping to the story, I haven't read the book myself but my girlfriend tells me it covers all the bases with some fleshing out to add to the minute count, which I think is more than excusable. Lastly, the animation. It does take some getting used to but as the film develops, the stop-motion becomes so vital to the way the story is told I really can't see it being done in every other way. Anderson, if anything, has an amazing stylistic flair that is the trademark of his features, and he transfers it to the medium with perfection.
There's a fantastic cameo from Jarvis Cocker, and Michael Gambon is brilliant as Farmer Bean. Personally I think George Clooney was puzzle-piece perfect for the role as Fox, the obvious choice being Bill Murray, who stars but just wouldn't have felt right in the spot of the confident and charming lead.
I really recommend going to see this film even if you have reservations. At least, you'll find yourself satisfied with the general pace and story-telling, but at best, you'll leave the theatre wanting to watch it at least 5 more times to explore the ever-present detail in the world Anderson creates.