Drupal has an option I haven't seen in any other CMS: You can set a theme for the admin section to your liking. As nice as it is, it raises serious UX problems especially for new users, if admin and frontend theme is the same (see UX study Baltimore: Where is my site?) There has been talk and action to cure this in a simple way: get a default administration theme into core.
Having learnt that core issues require determination and endurance, I'd like to make a fresh start (apart from an existing issue about that:(http://drupal.org/node/79023) by introducing some possible guidelines and candidates.
So what is this all about? Apart from seperating Front- and Backend optically, why should we want a seperate Admin theme and which requirements should it meet?
1. Clever use of Space
One thing that bugs me about Admin and settings pages in Drupal is the waste of space. Everything is rendered in a vertical manner, a lot of space is wasted because often only a third of the horizontal space is used. On the right see a typical example from the comment settings: the descriptions could easily also flow inside the red-lined area.