Why CoffeeScript rules?
- Sugar - coffee script has some highly useful syntax sugar: arrows, comprehensions, desctructuring, etc. You'll get used to those features in a week. You life will change. You won't regret.
- Less boilerplate - the amount of coffee code is in average 30% less than js code.
- Ruby-like style - some people like it.
Why CoffeeScript sucks?
- You have to learn it - though it takes from 2 days to 2 weeks.
- Awkward style - coffee is very ruby-like. Some people hate that style.
- You have to control non-printable characters - additional indent can ruin your code.
- No braces - indentations denotes the blocks.
- You can use it a team only if the whole team knows coffee - or you have to teach everyone and correct their style, listen to their moaning, etc.
Should I try CoffeeScript at all?
Yes, you should.
The investment of 2 weeks are worth it.
Some of those sugar will be included in ECMAScript 6.
As an alternative, you can use ES6 today.