I think a lot of people see frameworks like Ember and Angular and get scared by their vastness. You don't "get" them in one evening. I have spent many hours poring over documentation, articles and videos for both Angular and Ember and I still feel that there's more to learn. But things like routing, data persistence and controllers will be a part of your app even if you use React.
What I find good about Ember/Angular is that they are very particular about how your app should be constructed. When I started writing single page JS apps, I didn't know what the best practices were. If I had started with Ember, I would've learnt. If I had started with React, I would have been making it up as I went along. If you know what you're doing, maybe that's good. For me, I find that I really like having Ember tell me how to structure my app.
That's a very good point. I've currently settled on Backbone to give my stuff a bit more structure, but I suspect some of the complication of construction might actually disappear when using React. Not all of it, of course, but some of it.
You'll find a surprising amount of it will simply disappear. I'm at the point where I removed my models and collections directories entirely; since the only feature they provide me at this point are getting data from the server (which I can do with just jQuery, superagent, etc.)
In a simple React app (ie most apps), you end up storing all your models (as Javascript Objects/Arrays) in one single scope (the "App/Main Component"). As a result you don't need to share things around / access them / listen to them from many different files. They no longer need "managing". I hope that helps.
What I find good about Ember/Angular is that they are very particular about how your app should be constructed. When I started writing single page JS apps, I didn't know what the best practices were. If I had started with Ember, I would've learnt. If I had started with React, I would have been making it up as I went along. If you know what you're doing, maybe that's good. For me, I find that I really like having Ember tell me how to structure my app.