I think CoffeeScript seems nice in theory, but in the end, it's something made for people who want to code javascript, without actually using the language. It exchanges some of the terse, functional elegance javascript offers for a different kind of elegance, with its classes and inheritance and such like.
I won't say it's bad, as it is nice to work with when you're writing it, and I do quite like it. But I could never recommend it to someone who didn't have a good knowledge of javascript already.
I don't believe it exchanges any of the elegance. You can do the same things in CoffeeScript that you would in JS, just with less typing. That being said, a knowledge of how the browser will execute your compiled Javascript is crucial.
I won't say it's bad, as it is nice to work with when you're writing it, and I do quite like it. But I could never recommend it to someone who didn't have a good knowledge of javascript already.