[Achshar]

Actually chrome has this feature too. When you have saved a file once manually, it keeps track. So whenever you make live changes on the resources panel it live updates the DOM and upon clicking save, it automatically rewrites the file at it's original location. So it pretty much mimics the solution you suggested without any command line tools, extra file inclusion, downloads, etc. (http://www.youtube.com/watch?v=3pxf3Ju2row)

If you go up, you can read my comment in which i say why i dont like extra libraries, compilers for web work. (http://news.ycombinator.com/item?id=4219980) This is pretty much why.

And for the global mixin, (Which is pretty cool IMO, it really enables a lot more possibilities and creativity) you pretty much give the reason not to use them anywhere out side of practice work. 18 lines are huge. Plus css variables are pretty much on horizon, it is well worth the wait.