With Rok's guidance, I tested out the automated patch testing system that he's created. I uploaded a number of patches to his site, which then applied them to either Drupal 4.7 or Drupal CVS, and then ran 16 unit tests against them. We tried patches that applied and contained no errors, patches that didn't apply, and patches that had coding errors. Each time the test suite performed beautifully.
The value of this work is that patches that linger in the patch queue often fall out of sync with a moving HEAD. At the point when that happens, Rok's tests would be able to detect that and notify the patch maintainer. Furthermore, Dries, Neil, Gerhard and Steven would never have to write "patch doesn't apply" (after just having wasted their precious time trying to apply it). Furthermore, people often submit patches without thinking through all of the ramifications that a patch can have. If we were to build up a thorough set of unit tests (I can't imagine 16 tests really cover Drupal), then a lot of these errors would be detected automatically.
I can see this work adding significant value to Drupal on an ongoing basis. In fact, I can see this work being useful for any PHP project, not just Drupal. I'll be evangelizing about this excellent project. Rok is willing to give personal tours to those who are interested, and anyone who is serious about making Drupal the best that it can be should be concerned. So go try this one out... and good job Rok!