I saw Hugo in 3D today. I enjoyed it but I can understand some of the reviews which were less than glowing. Asa Butterfield who plays Hugo Cabret does not seem to have a wide range of facial expression, okay he has a very limited set of facial expressions. He can look determined. Many complain about the minutiae relating to film history. I enjoyed that part. I like films. I could probably watch this several times to catch little things that Scorcese added, like the Fantomas poster. Someone mentioned a person looking quite like James Joyce at a table in one of the opening scenes. True, these little things don't necessarily add to the cohesive whole but I liked it. From the book to the movie some of the scenes or actions and at least one character disappeared. I would have liked to see that character back but he wasn't totally necessary. Some characters and scenes were added. Some of those were good. Some seemed a little unnecessary. Some were obviously done just for the 3D.
How Hugo obtained the key was totally changed from the book. I think a whole set of emotional responses went away by altering this. And that he has Hugo instead of Isabelle unlock the back door to the theatre seems simply wrong to me. It takes away from Isabelle's character as developed in the book. She was more in the book and I think that was good.
I liked this movie a lot but it had a few flaws. Maybe I see them because I read both the book and the reviews before seeing the movie. I did enjoy their use in several scenes of Camille Saint-Saëns' Danse Macabre. I enjoyed the music and soundtrack overall but this, for me, was particularly enjoyable.
One other note, I have seen this movie mentioned as being science fiction. I have seen people suggesting it be nominated for a Hugo (funny, a Hugo for Hugo). However it was not science fiction. Such automatons did exist at that time. See this article on Maillardet's Automaton.