As someone who was just about to add some async.js to a CoffeeScript/Node project, I'd be very interested to hear about what problems you've had before I go and potentially do something stupid.

It might be just me, but

      async.waterfall [ 
        (callback) -> 
          callback null, "one", "two" 
        (arg1, arg2, callback) -> 
          callback null, "three" 
        (arg1, callback) -> 
          callback null, "done" 
      ] 

just doesn't make much sense to me. I just don't like the way it looks.

(code snippet from https://groups.google.com/group/coffeescript/browse_thread/t... )

Looks fine to me, but I do agree Iced can look even better.