Switching to React definitely has a learning curve, especially if you are coming from old-stool JavaScript or just not used to some of the concepts in React or Redux themselves. That said, once you get your head around it things start falling into place.

We're recently built a React Native app and I feel the benefits it brings to cross-platform development make that ramp-up worthwhile. A single iOS and Android codebase is a glorious thing, and helps avoid needing silo's of specialized developers.

I would say that the maturity (or lack thereof) is obvious when using React. The big ideas are solid, but there is a lot of thrashing - you need to watch each new version for backward-compatibility issues and carefully manage your dependencies. Coming from Ruby/Rails, I also feel like React is still at the point where you're spending a lot of time configuring things vs adopting standard conventions - it's getting there, and projects like react-navigation are helping build up that boilerplate, but certainly can be frustrating at times.