The Interaction Design and Information Architecture program at the University of Baltimore and a team of eight graduate students have completed a usability study on Drupal. The result is a great report (PDF) and an incredibly valuable video which they shared on drupal.org. It is too important not to share, so the video is also embedded below.
The results are consistent with the results from usability tests done at the University of Minnesota.
The results can't be ignored.
I printed the report, taped it on my wall, and I won't release Drupal 7 until I crossed of at least 90% of the problems they identified.