The second and final day of the sprint is over now. I implemented portlet reloading for the navigation and recent items portlet. This code is now easy to use from any event handler so refreshing other portlets is easy.
Another thing I did was to add information on what fields where modified by the Ajax call. This allows us to check in the event handlers if we need to update anything. The navigation portlet reloader is an example of how this could work.
At night (after the sprint) I finished the final bits by adding reloading support for the portal tabs and the breadcrumb. This was so easy to do that I made a small screencast as well.

Start screencast