I'll be the first to admit, I still find it a bit of an awkward syntax, and it was one of the parts of the syntax I kept bumping up against for the longest time. Amazingly I'm finally comfortable with it, but there is a kind of cognitive friction around that one. Personally, I blame whitespace significance. It's hard for whitespace to be both significant to syntax and formatting without impacting one or the other negatively.

The principle argument against whitespace significant languages is separation of concerns. Punctuation only for syntax and whitespace only for formatting.

That said the benefits of CoffeeScript still outweigh the tradeoffs for me.