CoffeeScript is amazing, I use it for everything including writing native iPhone apps (using titanium). Search for Album Plus in the app store. or visit http://www.albumpl.us/
For example, in my app (http://iphone.albumpl.us) I had to write a couple of small custom objective-c modules to get some camera/image stuff to have sufficient performance. But overall being able to write most of it in CoffeeScript, is so much better (enjoyment-wise and speed-wise) than having to write everything in objective-c.