Hi Martin, shared_files (aka MyFiles) will be seeing some enhancements soon.
It already has administrator level quota setting for students and teachers, and security should now be solid (in our latest code not in the current /contrib version) thanks to Petr's excellent critique.
It handles user-user file sharing and submits to the assignment module, users can set file access rights. It doesn't currently do file revision historys, etc. (but it won't over-write same name files, it will add 'copy# to same name files).
One of the features we're hoping to get working soon is integration with the editor, at which point teachers and students can have a central (course independent) file store they can use in various courses.
Toward this goal we have moved the file storage from moodledata/moddatta/modname/courseid/userid to moodledata/users/userid and the database keeps track of the permissions (this also has not been released to CVS yet but should be soon).
Thanks for the news about that block (and all your excellent Moodle PR around the web - it's very much appreciated!)