I don't like it because it doesn't even support getters and setters and will definitely lag behind for too long after new features start to become more mainstream. Other people don't like it because of many other reasons.
The point is, the libraries and snippets of code written in CoffeeScript are advertised in various communities like S.O. and GitHub as if they are written in JavaScript.
This is arrogant and needs to stop.
egecan, I noticed that you mentioned you are looking for an easy way to define getters and setters, have you checked out www.jTypes.com recently? We just added a new AIP syntax that makes it really easy to define getters and setters:
https://scontent-a-lga.xx.fbcdn.net/hphotos-prn2/1383208_385694174892987_509646233_n.png
You also mentioned that you don't like CS because it will lag behind for too long after new features start to become more mainstream. This is not the case with jTypes, as it plans to fully utilize many of the upcoming features found in ES6 (especially since it's emulating that behavior now). I just posted a more detailed description of everything here: http://www.echojs.com/news/6571
Lastly, as you touched on, CS is not JS, and should not be advertised as such. jTypes on the other hand is written natively in JS, and is simply a library that you include. If you're only looking for encapsulation, I would highly recommend jTypes Lite, and it is only 5 KB gzipped (14 KB minified).
I am always looking for feedback and suggestions for new features, so if you have any questions or comments, I would be happy to hear them and answer them!