To change the CSS you have to either:
- push new files to the application server (with a possible restart)
- recompile in the background (e.g.
compass watch on the server)
- get the server to compile on changes (using something like the example you gave)
Personally, I favour the first. I'm not sure why I'd want the server to compile static assets? It takes up valuable resources, and the CSS changes on my dev machine, so why not compile them on my dev machine? I've not heard good answers to these questions, so I use a Guardfile (or you could use sass watch or compass watch as a background task e.g. sass --watch app/views/stylesheets:app/public/css &) to compile them, and then I check in the .css files and push them to the server.
YMMV.