Initially it seemed fun and interesting working on extending MOBSA, but as I got into it, it quickly turned into a nightmare -- the class design is seriously flawed, and makes it virtually impossible to extend the functionality of the bundled Web Parts. We are talking about a complete reimplementation of all the Web Parts, just to implement a provider role. All the Web Parts also use a Table control to display the hierarchical data; instead of using an interface in the property definitions, they used the class. This also makes the job of adding a simple extra column to each of the Web Parts' tables a living hell.
If anyone on the team responsible for this product or if anyone knows anyone on the team, please contact me as I have a LOT of suggestions for improvements.