I migrated nearly all of troupeit.com over to ReactJS.

I really love it, but my biggest complaint has to be the mixing of logic and views together, and the duplication of security checks. Although I'm not entirely sure I can blame react for that, I blame my moving from CGI to Ajax/RESTFul interfaces for most of that pain.

We had about 90% of our codebase in RoR. In retrospect, I wish I had used Flux instead of React-Rails, but I didn't have that luxury as I was not starting from scratch.

As far as react and rendering data goes, I do wish there was an easier way in the render stack to conditionally display data. It's hard to squeeze logic into render()