A lot of people when they first learn about this project have a hard time understanding how it would be useful - so you're not alone!
I tweeted ([0]) about this briefly and thought I'd copy here for the benefit of readers in this thread:
> the wild thing about react-sketchapp is that we can now bootstrap designs with the actual code that powers the product we are designing
> it took me a little while to realize the paradigm shift. we normally think of the code / implementation as the end of the process
> this allows us to use production code not only for our production clients, but also for starting the next iteration
> react being decoupled from the underlying UI implementation unlocks a lot of possibilities. this is just one.
> we are starting to view our react components for our design language as not just an implementation, but as the specification itself
[0]: https://twitter.com/intelligibabble/status/856941689029640192