It's not enough to say that I disliked this movie because it wasn't like the book. As a matter of fact, the filmmakers discarded virtually everything that E. B. White created, including the charm of the matter-of-fact tone he used in writing about a mouse who was born to a human family. White gave us a sly and subtle fable about growing up that has been loved by many generations of readers. It took a lot of nerve for these guys to throw all that away.
Judging from the box office results, you might conclude that they replaced White's story with something even better. Ah, but that would be to grossly overestimate the taste of the American public. People will go see any sort of trash if it has a famous name on it. Imagine, if you will, a garbage scow christened The Queen Mary. They changed every character, including Stuart himself, who is no longer urbane and resourceful, but merely mouselike. They made him an adoptee! They put in a low-level-Disney plot, with lots of animatronic action. There's no real story (certainly not one that makes sense anyway) - only a series of gags, most of which don't work.
The bottom line: do not go to this movie if (a) you've read and loved the book, or (b) you have any taste in movies at all.