Significant whitespace is used instead of braces to delimit blocks - a fact that will keep discussion forums buzzing, although it is in line with other recent languages like CSS3 extension Sass, Haml, etc.
CoffeeScript has been around for about a year, and has recently gained exposure through a few public projects that used it. ArsTechnica's iPad application is written using HTML and CoffeeScript and runs as native application using PhoneGap. 37Signal has published Chalk, a whiteboard app that runs on the iPad and uses HTML5 features, such as the Cache Manifest, to run offline. It also uses CoffeeScript.
C and C++ code can be translated using Emscripten and the project's site has a few demos of translated C and C++ libraries. However, it also has demos of translated versions of Python and Lua runtimes.
Significant white space !#@!
This and other experiences confirm my feeling that significant white space are not a good idea.
I don't know anyone who really tried Python for more than a day...
Re: Significant white space !#@!
I think there are some advantages to using indentation to denote blocks.
(1) There is no way to munge the code to minimize whitespace. This was a technique meant to reduce data transfer overhead in the days when transfer speeds were problematic. Today, code readability trumps transfer speed optimization (at that level of optimization, anyway). Obsessing over whitespace is now an anachronism.
(2) Also related to code readability: The ending delimiters for code blocks are just visual clutter. It's easier to see what's going on in the code when blocks are clearly called out by indentation.
Just one opinion, of course.