Seriously, there needs to be something that shows the way to the future. The people working on the next version of ECMAScript look to languages like CoffeeScript as archetypes of the future.

More then anything CoffeeScript shows us what Javascript might look like someday.

We get to actually try out new idioms and see if they work for us. If they don't we have ample time to voice concerns. This is a huge departure from the past.

If anything CoffeeScript will make Javascript better.