I feel with this, Frozen, and Wreck-It Ralph, Disney is really entering another golden age (I know, all the critics say that...), which makes me happy despite all my issues with Disney because Disney is so much of my childhood. I was afraid Big Hero 6 was going to be too pop-culture-referencing and wink-wink-nudge-nudge, as well as being afraid that the main character would annoy me (that's my biggest issue with How to Train Your Dragon) and that the blend of San Francisco and Tokyo would feel pasted on and Orientalist. Instead, it's a really good movie that made me cry more than once, has some great relationships, and did what I thought was a pretty impressive job of balancing gender roles and portrayals as well as having POC representation.
(That said, Disney, I will be so happy if you make your next geek-oriented movie with a female lead!)
Also, the marketing department did a really good job with the trailer; I think it only goes into the first half hour of the movie and doesn't let on to some pretty big things while keeping the overall tone of the movie.
What most impressed me about the trailer was how the first ten or fifteen minutes of the movie completely recontextualizes a lot of the scenes, so even if you've seen them a lot, there's more there when you see them again in the movie. As I mentioned, I was worried I would be annoyed at Hiro, and I kind of was... and then they introduced another character that helped a lot. Then when something happens and Hiro gets acquainted with Baymax the robot, it adds a new emotional layer to all the boy-plus-robot scenes from the trailer. Also, Baymax is hilarious and adorable, as the best companion robots seem to be. (Are there any girl-and-robot stories that mix coming of age with teaching your robot how to be more human or something? Boy-and-robot seems to be a distinct subgenre, with this, The Iron Giant, Terminator 2, and probably more I can't think of right now.)( Cultural appropriation, gender, and other considerations )
I am talking a lot about the more political aspects of the movie and not focusing on just how fun the movie is, I think partly because so much of it is in the background and not that noticeable if you aren't looking for it. I thought this was a really great example of how to have diverse characters and places and make it feel organic and not the central issue of the story, and it's what I would love to see more of, especially in genre stuff.
A lot of the reviews I've read were tired of the whole superhero thing, but I did not realize it was a superhero movie going in (I had it more pegged as an Iron Giant thing), so when Hiro starts seeing everyone as a superhero team, it totally cracked me up. Because if you are a boy with a giant robot and a 3D printer, why not?
And finally, I LOVED how the entire movie was a celebration of engineering and science and making things; one of my favorite parts is Tadashi showing Hiro his "nerd school" and how clearly he loves it. I feel I should say so much more about this, because it was a huge part of why I loved the movie so much (that, and the Tadashi-Hiro relationship) and I've spent so many words on the background stuff. Except I don't really have anything outside of how much I love it and how much they made an effort to show that the whole maker culture thing isn't solely a white guy thing.
On a completely random note, I'm amused by the Disney-Pixar-Marvel mashup so that the movie has the now-famous animation short a la Pixar and the post-credits scene a la Marvel.