We've been playing with this architecture. It makes testing a lot easier - you just shove data in where needed and things pop out the other end. It also forces us into splitting things up in a more sensible manner. Along with easier testing is easier reasoning.

That said, like most new architectures/frameworks finding a big example (not just a TODO app) is really hard. We are currently prototyping a big app using React/Flux and we find ourselves having to question ourselves a lot more than we'd like.