Question from a JS layman: React is great in comparison to what? vanilla JS? Angular/Backbone/Ember? JQuery? any other *.JS? Also is this a good direction for "mobile first" approach? What about platform independence? (iOS/Android/Desktop agnostic, etc, etc). (bootstrap? phonegap?)
In comparison with Backbone/JQuery, React is more declarative. It encourages the developer to describe the structure of the UI in a given state and let the engine handle the transitions between states. It's possible to use Backbone models and events with React views with very little impedance mismatch.
I would like to hear an Ember expert's perspective.
React Native has an interesting approach to mobile-first development. The general philosophy is "learn once, write anywhere" instead of "write once, run anywhere". Most apps cannot make the most of their platform while being truly platform-independent, but unifying component lifecycle behavior between platforms could end up being easier on developers than learning the particulars of each platform, while producing a better result than a PhoneGap-style wrapper.