Lots of good code and discussions this week.
I have structured out how the revisions API will look, and now my goal is to finish those up and check them in over the next few days. I have decided on a preliminary storage schema as well (two post types and a taxonomy), and based on the API and how I need to query different objects, I will decide whether I will want to add a third post type.
I also plan to commit some nifty third-party stuff this weekend, namely diff creation and viewing, and real-time syntax highlighting. Then it comes down to integrating the revisions API with the editor itself, then sandboxing and figuring out the UI.