I presented a session on "Essential Drupal Modules" at today's Boise Code Camp. The talk highlighted the modules most every Drupal installation should have, as well as a number of gap-fitting modules that fill a few UI and functionality deficits found in Drupal core. Additionally I included a segment on finding and evaluating modules.
If programmers wanted to be technical writers, they probably would be technical writers and not programmers. You can see that tautology played out in many a Drupal module where the documentation (most likely a README.txt) is on the light side, and the code is on the heavy side. Don't get me wrong, there's some great documentation out there, and many valiant efforts on the part of developers, but you just can't always depend on extensive documentation - especially when you're looking at a module that's not particularly mature.
Sometimes you want to measure how much you've contributed to Drupal.
Sometimes you want to measure someone else - perhaps you're considering hiring this person.
Try the following Google search (where "username" is the person's Drupal.org username):
That's it. Not scientific or anything, but it'll let you get a handle on how often a person's username appears on http://cvs.drupal.org.