There is a need for Coffeescript; programming Javascript directly leads to cross-browser issues. Something like Coffeescript can abstract away the per-browser style issues. (The main annoyance I notice is the behavior of trailing commas in lists. In Firefox, it works. In IE, it silently breaks. Coffeescript avoids this issue, since the code you type never sees the browser.)

I would personally find a Javascript->Javascript compiler more compelling, as it would mean I wouldn't need a new editor toolchain. But that wouldn't be as fun to blog about, becuase you would still have to type $("DOM") instead of $ DOM!