The concern I have about movie adaptation of children's books is that some books are really short and quick to read and it is up to the producers of these kinds of movies to fill up a suitable running time of around 78 to 90 minutes. This is usually where things could go awry (The Grinch Who Stole Christmas and The Cat in the Hat come to mind).
Oh my gosh, I am so excited. I think it will be ok. Maurice Sendak has made the book into a play or opera so I think the author will have a good bit of weight as to what happens in the film.
I love Maurice Sendak he is my favorite children's book author.