Coming soon to the Intelligent Book is an update to the way that content is edited to support real-time collaborative editing. If two people edit the same page at the same time, they will see each other's changes as they happen. (Well, with maybe a 30 second delay.) This is a way of editing that users have become used to with sites like Live Workspace, Acrobat.com, and Google Docs.
The code is actually already in the Intelligent Book, I just haven't turned it on yet. One way of thinking about it is that it does docs with TinyMCE. The same code is also intended to go into the Sakai 3 content management system, so I've set up an open source project for it called Docwit.