(Mild spoilers below.)
I'm in in the minority on this, but I was disappointed with Inside Out.
There is no question that Pete Docter has the ability to emotionally affect an audience. My problem with this film, and on reflection with Up, is that he focuses too much on invention, and it gets in the way of the characters and the story.
In Up, everyone remembers the montage of Carl's life with Ellie. Nobody talks about the absurd age and inventions of Charles Muntz.
In this film, what people will take away is the characters inside Riley and the ending, but the world they inhabit is overly complicated. There is an lengthy journey for two of the characters inside Riley's head and there are all sorts of rules of the world that are introduced too conveniently. Characters and props appear during the journey that change the audience's sense of what is possible and what is not. It's hard to generate suspense when you never know when the equivalent of a magic wand will show up to help the characters.
The problem is structural. The film makers had too many good ideas to fit in the beginning, and so by introducing them mid-film, the world was continually redefined to the detriment of the story.
Here's a spoiler. If Joy can be sad and cry, why can't the other characters inside Riley's head go beyond their dominant characteristic and grow as well? The problem is that if you have characters who are incapable of change, you have no drama. But introducing change into one character reveals the other characters as nothing more than stereotypes, no matter how entertaining.
The solution would have been to spend more time outside Riley. Because she contains conflicting emotions, it's natural that the drama should have played out there. But Riley is a puppet who can't experience emotions outside of what the characters in her head allow. While her experiences moving to a new city, entering a new school and screwing up in front of peers are all easy for the audience to empathize with, they are done in a perfunctory manner. We never see her interacting with the others in her school and so her experiences are left at the level of the generic.
Inside Out contains a lot of good character
comedy, inventive concepts and striking design. However, the dramatic logic of the film often gets broken under the weight of those things, and that's why I find the film unsatisfying.