Is that code really valid CoffeeScript? Last I looked, and I admit that the last time was months ago, 'on' was a reserved keyword (an alias of 'true') and I had to do some quite ugly hacks to be able to have a method named 'on'. This may have been related to dynamically adding the method onto the prototype of some constructor rather than defining it in a class.

Besides that, I still get feelings of discomfort when thinking about rewriting JS to coffeescript when knowing that the compiler will just write it as JS again.

EDIT: Tried it. In this case it seems to works.