Nice, I really like this plugin. What is on your roadmap for the future?
I've given a lot of thought about the sharing of documents in a WP-based intranet setting and generally the excellent WP Document Revisions plugin comes to mind (though that plugin doesn't have a built-in front-end).
WPDR is definitely suitable for corporate documents and your plugin is perfect for personal- produced document sharing. WPDR takes advantage of a lot things that WP does organically like revision editing and so forth that are great for the corporate environment.
While I can't see it know or envision how, I'm wondering if there is a way to make your plugin compatible with WPDR, or have the two integrate or at least compliment each other in some way. Between the two plugins, I'm thinking document management powerhouse within WP/BP, but figuring out the details of what and how is something I can't quite envision yet.