> I worry the compression, while cute, could start to get a little extreme after a while

Not my experience. I love how short my code is. http://www.paulgraham.com/power.html

> there seems to be some interesting inconsistencies

Yeah, there are. These bug me less now than they did initially. Like any language, you have to know it well to use it well. But there's much less that you need to know about CoffeeScript than about, say, Ruby or Python. CoffeeScript's feature set is small enough that you can master it very quickly.

> is there a clear unambiguous grammar for it anywhere?

https://github.com/jashkenas/coffee-script/blob/master/src/g...