"Being able to do everything with a single language is kind of a big deal for many companies;"
Its a shame that so far JavaScript seems to be the only language you can use on the client and server. I come from a Perl background and every time I try to do something in JS it seems like a kludge.
I don't have experience with ClojureScript yet, but CoffeeScript is trivial to debug since the source and the compiled JavaScript are structurally very similar.
On top of that Python has a solid set of libraries for it. In my experience with JavaScript (admittedly a lot more limited than with Python or Perl), the library support is far poorer. Angular is one of the most popular frameworks out there and the documentation is terrible. Compare that to any major framework in Python or Perl and you will see the difference.
IIRC, JS was designed and initially implemented by a single programmer in about 10 days.
It's far better than could reasonably be expected given that, but it still sucks. Some of the things that immediately come to mind WRT not being well thought out are bad number handling, lack of modules, and possibly the number of warnings needed about how "this" behaves.
Its a shame that so far JavaScript seems to be the only language you can use on the client and server. I come from a Perl background and every time I try to do something in JS it seems like a kludge.