So I've learnt a fair bit of JS and now I just can't be bothered to write in CS, JS is really not that bad if you understand that JS is NOT class-oriented and CS ends up only obscuring reality, not altering it. Which brings me back to why I had to learn JS in the first place.
100% of what you learn in CoffeeScript is applicable to Javascript, and viceversa. The real pain, is like you said, debugging applications. I can't just write coffeescript into the console, not even a little`console.log`which is infinitely nicer without the parentheses.
There's a great free e-Book hosted on GitHub that is written by Alex MacCaw. I recommend checking it out. Here's the link: http://arcturo.github.io/library/coffeescript/
Learn JS and learn to write good JS! I personally hate CS because I some people take that route to avoid writing clean JS, just because CS looks nicer. Once you truly learn how js works, migrating to CS will be very simple.