I'm an early adopter and implemented a mid-large single page application using the Facebook Flux library.
As I'm a little late to the conversation I'll just point out that despite my best hopes Facebook seem to consider their Flux implementation to be a proof of concept and it has never received the attention it deserves.
I'd encourage you to play with it, as it exposes more of the inner working of the Flux architecture which is quite educational, but at the same time it does not provide many of the benefits that libraries like Redux provide (which aren't that important for small projects, but become very valuable for bigger ones).
We have decided that moving forward we will be moving to Redux and I suggest you do the same ;)