We've built a product in coffee-script that is made for navigating websites and forms logging and scraping and pulling in data.
It's quite useful outside of rails in that sense I'd say. It could have just as easily been done in JavaScript but I'm not a fan of the syntax(fuck curly braces)
I'd maintain that just about anything out there can be used outside of the context you think of it in.
Asking if coffeescript is useful outside of rails is similar to asking is perl is useful outside of scripting, it's a poor and misguided conception that languages can only be used in a certain way or with a certain tool.
I'd say that's true much more often than not that if you know a language well you can build complex applications with it.
I would recommend against using any CoffeeScript before you're proficient with JavaScript. It can be a great boon to productivity, but if you don't understand what it's doing underneath you'll shoot yourself in the foot a lot.
CS support is built-in to the Play! framework (Scala). By that I mean that it detects your CS files and compiles them for you as needed, then puts the resultant JS where it belongs amidst your static resources.
The presentation is very well put together, but CoffeeScript is a hack built on top of JS in order to use Ruby semantics. You're correct in that it's not really used outside of Rails, and not knowing JS proper (not that I personally recommend using it for much more than jQuery and a couple other libraries, when you absolutely must) poses a problem for when someone runs into the 97% of code that is JS.
"Not really used outside of Rails" - Do you have any source to back that up, or is it simply what you've seen? I first used CoffeeScript in a Python shop, personally.
