a) does line-for-line output so it's easier to debug b) can handle normal JavaScript, so it melds with existing code c) progressive enhancement, adopt features at your own pace d) the option to shadow variables using var e) declared function support
AFAIK the creator did work on CoffeeScript for a while but decided to go in a different direction.
There are plenty of different alternative JavaScript dialects out there, from new ones like Kaffeine to ports of popular languages. http://altjs.org/