irony alert: Brendan Eich has said publicly that CoffeeScript was the impetus for several of the features that made it into ES-6, like fat arrows.
Without CoffeeScript, lots of people wouldn’t have known that they wanted some of the things that are in ES-6.
As it is, you don’t need CoffeeScript to develop for Atom. Which is part of the beauty of CoffeeScript. It’s interoperable with what you’re doing today.