I think we need to. It deserves a credit, because we use it and we didn't pay for it. CoffeeScript makes our lives easier, almost eliminates bad practices and removes brace clutter from the screen, making the code more readable, understandable, better.

When having to choose between a library written in JavaScript and a library written in CoffeeScript I choose the latter, because it statistically has a probability to be a better library, just because the coder didn't have a chance to use bad JavaScript practices, when writing it. Assuming I usually don't have time to read the code of the libraries I'm using.