I use CoffeeScript whenever requirements permit. Recently I've been working on a small side project using ES6 (via iojs) and I have to admit that it's pretty refreshing to see JavaScript take on some modern improvements and it's clear that today's CoffeeScript loses out on critical functionality that ES6 brings to the table.

With that stated, I still overwhelmingly prefer CoffeeScript's syntax to ES6. I'm glad ES6 took some inspiration from CoffeeScript, and Babel is a great way to bridge the future of JavaScript over to client's of the present, but I'll always prefer the CoffeeScript syntax for white-space sensitivity, support for optional semi-colons, optional parenthesis for function calls and optional curly braces for object literals. I don't need those features but I really like them. For me, the real future of JavaScript is a re-imagined CoffeeScript that takes on some refined semantics in order to bring ES6 feature support into the CoffeeScript compiler. Admittedly, that is not a simple undertaking (though I'd imagine the code would be simpler as a whole since it would necessarily trash obsolete features like pseudo-classes etc), but I know I'm not the only person who would love something like this.

I don't know how jashkenas is feeling about ES6, but one day I'll have my ES6Coffee, even if I have to brew it myself.