I've been using SASS and Compass for close to a year now, SASS particularly with compass, is great for CSS authoring. Some of its key features like nested selectors, variables, mixins and functions are now invaluable to me.
Installing and using SASS and Compass is fairly simple and easy on Ubuntu or any other OS for that matter, but since its a command line application it has to be used from the terminal. Using it from the terminal is fine and most of the time we just need to use the compass -watch command to auto detect changes and compile sass files to css. But its always nice to have a nice and clean GUI app that can do all the work for you.
Compass.app is a front-end for Compass, and is written in Java(Jruby) so it can run on Linux, Mac and Windows. The app itself is not free for download, but since the developers have made it open-source you can legally compile your own copy by downloading the source from their git repo.
Download the latest copy of Jruby from here
Open a new terminal and run the below command to install rawr package manager
Clone the Compass.app source from github
Change Directory to CompassApp folder
Finally compile CompassApp
Once the compilation is finished you should have the compiled app inside CompaassApp/packages/linux run the run.sh file to start the app.
Update: Download and run this script inside the folder CompaassApp/packages/linux. The script will move compass.app folder to your home and create a .desktop shortcut for accessing compass from your unity dash.