On my way to Drupal.org to check on some updates to modules, I ran into the latest report on Drupal usability. The report, in video and PDF forms, is the result of some testing done at the University of Baltimore. It seems to confirm and complement the usability study done here at the University of Minnesota.
Check out http://drupal.org/usability-test-university-baltimore-community-solution... for the full story.
I recommend this especially to anyone who creates Drupal sites for clients, even if the "client" is your own organization. Seeing what people new to the Drupal interface see, prior to being oriented, is very instructive.
I also recommend skimming the threaded discussion that follows the offical report node. Interesting comments, some insights into Drupal 7 (!) and other insightful goodies therein.