Thanks! It looks like a full-featured solution, and it's even a commonJS module.
Thing is, that CoffeeScript solves the most common pain though (the *.prototype syntax), and the chasm between that and interfaces, singletons, private members, etc., might be too big for the standard use case.
As of ECMAScript 5 you can build inheritance chains without constructor functions and *.prototype objects. It is simple enough without any framworks (https://gist.github.com/1558929) and it is just a bit more verbose than CoffeeScript classes (https://gist.github.com/1671263)
