There's a key scene halfway through Hugo's journey where it is explained to him that there are just some things that he's too young to understand, and I can't help but wonder if that might be true of the audience at which this very mature, very visceral journey that Scorsese has painted for us is aimed. This film moves at a rather slow pace through the first half, if not 2/3rds of the tale, but the payoff is all the greater for it, assuming you're old enough to appreciate the history being portrayed. I imagine there are plenty of kids who have seen it already who were expecting something a bit faster paced and closer to what they are used to, and were disappointed. Most of them probably don't even realize that it's actually based on (loosely, but rather accurately at the same time!) the real life of Georges Méliès, who was known as the "Cinemagician" because he was, basically, the father of "special effects."
So wait, you might ask... Is this a film about a kid named Hugo, or about the early days of cinema?
And it's wonderful. It truly is a love letter to cinemaphiles, and I'd rather not give away any more than that, because that's only slightly more than I knew going into it, and in my experience, the less I know about or expect from a movie, the more likely I am to enjoy it. Just know that you really should see it in 3D. I know people are tiring of it lately, but it really does play an integral role in this film, and if nothing else, your eyes will thank you.