Ernest has done quite a lot of experiments with his collaborative editor. Early on I've advised him early on to focus on the communication/collision detetection/... part as opposed to a new really fancy editor.
We've seen explosive growth in 2005 and 2006 based the ability for Drupal sites to rapidly deploy new features that meet real world customer needs, not just fulfill technical requirements.
Today I spent some time on themes.drupal.org. I upgraded it to the 4.7 branch, skinned the Drupal installation completely and removed some lesser used features.