We use it at $work in an "isomorphic" context along with react-router[0] and fluxible[1]. I'm very happy with it and the ecosystem developing around it. Using React also provides an interesting lead-in to native apps with react-native.

We transpile all of our JS with babel as well. I'd be happy to answer any more specific questions as well.

[0]: https://github.com/rackt/react-router [1]: https://github.com/yahoo/fluxible