Overall react-koans served it purpose and I at least could make some assumptions how it works at least how I think it does some things. As for the koans itself. They were interesting and not overly complicated. But I do believe some of the descriptions could be clearer. And errors displayed by tests could be in some places more helpful at least for a beginner like me. But the whole experience with it was very positive and I do recommend you to check it out if you want to learn a little bit of React.
As for React and my first thoughts about it. First of all, everything I will write here is my opinion after just React koans and nothing else, to be honest, and probably is not accurate or simply completely wrong. But well those are my first feelings about it.
What I think is cool in React at least after finishing koans is that each component on a site is treated as a seperate object and all of it functions and states are described inside closed section.
The second thing I noticed and liked is that it seems to do just one thing and that its. It doesn’t try to be complete front-end frameworks from what I see and heard like ember or angular.