[btown]

Fiber is simply a fully-backwards-compatible performance enhancement, though that does it a huge disservice. It's actually figuring out how to run different parts of a render() function in different clock ticks, essentially making renders asynchronous so that animations don't jitter or drop frames, and different parts of the render tree can be prioritized out of order. Unless you were doing weird stuff with low-level animations or React internals, user code won't need to change, but it will instantly become buttery smooth. See https://github.com/acdlite/react-fiber-architecture for how.

Now, the preference for stateless functional components that has been popularized for user code by Redux is certainly a trend, and a focus of performance attention. But that's nothing new.