Just read Kristjan Jansen's blog: Drupal UI challenges: my pre-Drupalcon rant. I can claim this is the best Drupal-Usability article I ever read. If you are either Drupal user or usability apprentice, this one is a-must-read.

Kristjan quickly goes through the root of Drupal usability messy:

We need "Drupal UI Police" what provides law and order in this rebel countryside. We need a good Drupal Human Interface Guide

It's damn true.

GNOME faced this problem long time ago. Then GNOME HIG was introduced in GNOME 2.something (2.2 or 2.4?). Now GNOME is one of usability-wise desktop environment. Simplicity and consistency over the place.

Do I mention the usability inferno in cough KDE cough?

When the project is large enough, there must be time to shift the hand-crafted interface to industrial process. Now Drupal reaches that point.