I looked at 6to5 and started re-writing a few files of CoffeeScript in ES6. First impression was not great. I'd forgotten how many curly braces are required in JS. ES6's fat arrow is just not as nice as CoffeeScript's (required parentheses, no option for thin arrow). I'll no doubt try it out again soon, but I'm not a convert yet.
ES6 fat arrow syntax doesn't require parentheses if there is only one function parameter. If there are more, parentheses make the code more readable in my opinion.
