Groups as Roles through Taxonomy Access Control

Searching for the best way of rolling out a complex multi-site, multi-group framework for an international NGO, we have developed a solution based on roles and taxonomy access control which we find clean and powerful. We want to share it in detail with the Drupal community (1) to test it and see whether it stands up, or whether other Drupallers tried it and found it wanting, and (2) in case it is of help to others in the community. We have written a detailed tutorial at http://drupal.org/node/200631, dealing first with the Groups functionality, and are working on a second tutorial which adds in the multisite functionality. We'd be VERY grateful for feedback. Thank you!