How about improving coffeescript language? I tested in on a small project recently and run into lot of ugly edge cases, where I had to read the generated code to find out that coffeescript compiled code differently than my expectations were?

example: http://t.co/omIdeNGA (jQuery chaining)

  # I'd expect these two blocks ...
  
  $output
  	.html 'a'
  	.prepend renderedHtml
  
  $output
  	.html ('a')
  	.prepend renderedHtml
  
  # ... to generate exactly same code as this:

  $output
  	.html('a') # you cannot put whitespace or omit parentheses here - but in other places, you are guided to remove them and use spaces
  	.prepend renderedHtml

Coffeescript:

  $output.html('a'.prepend(renderedHtml));
  
  $output.html('a'.prepend(renderedHtml));
  
  $output.html('a').prepend(renderedHtml);