I don't know where to draw the line exactly, but I wouldn't call them completely new languages. Coffeescript is basically another syntax for JavaScript and Objective-J adds a few bits of syntactic sugar. The latter, of course, is pretty equivalent to what Objective-C does to C, Coffeescript reminds me a bit of Ratfor.
Considering the unstructured default nature of JavaScript and its flexibility, I would say that you can get much farther of the trodden path by just using certain libraries. Adapting to a different syntax that just expresses things slightly different/shorter than you'd usually do things isn't as hard as actually doing things a different way. Straightforward jquery written in Coffeescript should be easier to understand than code that heavily uses wu.js, underscore and/or js.class.
Of course, Objective-J has both syntactic additions and a huge Library tacked on. It's more meant to people who already work with Cocoa, so that their adjustments have to be minimal than for people coming from JavaScript.
Coffeescript doesn't really compare to that. It's actually pretty minimal, and you shouldn't have trouble using it with JavaScript libraries, unless they depend too much on certain syntactic stylings (I bet fab.js won't play nice).
Considering the unstructured default nature of JavaScript and its flexibility, I would say that you can get much farther of the trodden path by just using certain libraries.
Wu.js (thanks for the link) still looks like Javascript to me and won't cause any problems with Firebug or Emacs. Coffeescript and Objective-J have a completely different syntax. I can believe that Coffeescript is easier to read but it doesn't seem like enough of a win to break tool support and to work in two completely different syntaxes (inevitably there will still be plain js to deal with in most projects).
Objective-J seems even riskier. I can see the appeal for Cocoa people but you're really going all-in with that kind of framework.
Yes, Cappuccino is an all or nothing framework, it's not meant for interoperability with other JavaScript libraries. You'd have to like the whole deal.
I don't have a big problem with switching between CoffeeScript and regular JavaScript, though. I'd regard it as some kind of shorthand for writing code, similar to what more elaborate template languages (haml etc.) do to HTML. It doesn't do weird transformations (last time I looked at it), so you should be able to debug the produced code.
Right now, I'm not using it in any production code, as for simple client-side programming with JQuery, it's not a big win. I'm seriously considering it for a future node.js project, though. I found myself using too many snippets when writing JavaScript code, which reminds me to much about my last Java projects…
Considering the unstructured default nature of JavaScript and its flexibility, I would say that you can get much farther of the trodden path by just using certain libraries. Adapting to a different syntax that just expresses things slightly different/shorter than you'd usually do things isn't as hard as actually doing things a different way. Straightforward jquery written in Coffeescript should be easier to understand than code that heavily uses wu.js, underscore and/or js.class.
Of course, Objective-J has both syntactic additions and a huge Library tacked on. It's more meant to people who already work with Cocoa, so that their adjustments have to be minimal than for people coming from JavaScript.
Coffeescript doesn't really compare to that. It's actually pretty minimal, and you shouldn't have trouble using it with JavaScript libraries, unless they depend too much on certain syntactic stylings (I bet fab.js won't play nice).