This is a fantastic idea and I'm really excited to start using this - I wanted to develop this kind of program for a while.

This is my use case: I work with designers who are hesitant to use git and make changes really quick and test them on a live WP or similar site. Often times we have two or three people needing to edit a single css file and everyone has to open/close the file often to not overwrite the changes of others. Maybe there is a better workflow, but a collaborative editing tool like this will go a long way in streamlining this process.