I usually introduce CoffeeScript as "shorthand for best-practice Javascript".

The big weakness of CoffeeScript IMHO currently is the weak organizational structure of the community. I don't see a clear path where the project is going, and already there are forks/parallels like livescript and IcedCoffeeScript, both with their own strengths.

The output is usually more readable than a lot of JQuery plugins I've seen ;-)

I regard CoffeeScript and its cousins as tools rather than frameworks or languages.