I can't speak for you, but where I can, I like to use CoffeeScript because:
- it makes my life easier by helping me avoid basic errors like using ==
- it looks and feels more like Ruby which means I don't have as far to go when switching contexts between Ruby and client side code
- I don't have to do bizarre things like create self calling functions or functions that sit in between public and 'private' methods just to obtain some degree of encapsulation**
- jasmine specs look lovely vs eeew!