I can't tell you about any essays, but from installing and checking out different CMSes over the years, I still really love the DNN admin UI. It really is done very well. It's worth checking out as it is very intuitive and easy.
Joomla is total insanity by comparison.
Wordpress is mediocre comparatively, but certainly better than Joomla, which is hard to be worse than. (Though I did write a CMS in 2001 or 2002 that sucked pretty bad for the admin UI, and was worse than Joomla aesthetically, though functionally it did what it was meant to do very well for even users that suffered from near brain-death.)
The Host/Admin/Site concept works well in DNN. Permissions are also very good with Portal, Site, Page, Module, and module internal permissions.
However, like every CMS out there... DNN suffers from the same idiotic notion that you only need 1 database user for the entire application... But that's not about the UI/interface, and just an internal pet peeve of mine.
There are some CMS review sites out there, but I'm guessing that you've already been over them.