James Strong's Profile

In my opinion there is one huge advantage to Coffeescript that hasn't been discussed at all in the comments, and that is that Coffeescript introduces OOP to Javascript.

O.k. Yes, you can do the exact same things you do in Coffeescript just natively in Javascript, but unlike some of Coffeescript's other 'improvements' that just remove a few brackets or parenthesis here and there, Coffeescript's OOP model turns what would otherwise be incomprehensible and arcane code into beautiful, readable, understandable code.

http://jashkenas.github.com/coffee-script/#classes

Once I started taking advantage of Coffeescript classes, I found myself writing Javascript in a totally new innovative way that I had never done before. It isn't just about what can or cannot be done with or without Coffeescript, but more about what Coffeescript inspires you to do through its easy classes and extension framework. You start thinking differently.