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 () 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
This is exactly what I'm doing with Semantic UI React. I'm prototyping in React, and building my own visual language on top of the visual language of Semantic UI. I see how I could instead render my components to Sketch instead (if a really great Sketch file with all the Semantic UI components existed).