For not using Javascript itself, that is widely understood across the programming community, that is not perfect but either not a disaster as a language, I would expect a lot more gains from a to-javascript-compiler. Here what I see is that there are a few semantical changes and syntax changes, but for me this is not enough to switch.
What I think the value of CoffeeScript could be is to show how Javascript could be improved in the next versions.
What I think the value of CoffeeScript could be is to show how Javascript could be improved in the next versions.