Ebert's puzzling review, which is favorable in content, but less than enthusiastic in tone, seems to complain that the movie is not a book, and that the movie has more scenes of action than the book. He also thinks that too much of the action is carried by the non-Hobbits, but this is the case in the first book of the trilogy also. This is puzzling in a professional critic, who obviously knows that a movie can't be judged as literature.
I certainly did not see it this way. Elijah Wood was superb. And he played the role well. And Jackson's adaptation kept him in the forefront. I was actually surprised to see how much these feisty little hobbits did battle against the cave troll. Ebert is seeing something I surely don't.