I'm relatively new so I can't speak to the original rationale, but right now it fits our needs. I'd love to do some ClojureScript (or just ES2015 through Babel), but right now we're focusing on building stuff instead of playing with languages :)
> ...but right now we're focusing on building stuff instead of playing with languages
Which is exactly what's so compelling with regard to ClojureScript and say Om or any one of the React wrappers out there: you guys already use Clojure and ClojureScript and its libraries are incredibly pragmatic and designed for "real work". CoffeeScript would seem more like language play than ClojureScript, but of course I'm speaking as an outsider. :)
Also if you haven't already, take a look at David Nolen's recent talk on Om Next[1]. Personally if I were using Clojure on the backend, I'd be pushing hard for it on the frontend too.
Personally, I'm not a big fan of CoffeeScript and it's something I brought up when I started, but at the end of the day you can write good and bad code in any language. I've watched that talk and found it really compelling, but I'd sooner get rid of Backbone than change languages. I've been following Dan Abramov's stuff pretty closely, the refinements in Redux seem to take the best parts of Om and Flux.
Just want to point out that I personally don't think Babel/ES6/ES2015 is ready for production yet. I just wrote a small library with it and ran into several hiccups with continuous integration, which was fixed by specifying a specific node and npm version of which both were I think just the default linux packages. If I ran into problems scratching the surface I can only imagine what headaches a deeper usage could cause. I realize this is a bit off topic, and would be interested to hear from someone whose done it, but I wouldn't want anyone to jump in head first and hit the bottom of the pool..
