Definitely not the prettiest system out there, either in terms of admin UI (which is spartan) or templates, but the code is a thing of beauty. Whether this has caused its user base to be relatively geek-heavy or is a result I can't say, but either way a technically proficient user (or at least one who is willing to become one) will find plenty to admire.
The installation went off without a hitch on OS X.2.6. The only trouble was that my ISP blocks port 25, so I had to configure a scrip (available in the Drupal CVS) to handle an SMTP connection to my ISP's server. While it definitely requires some PHP knowledge, it was as straightforward and well-explained as I could ask. Moreover, the Drupal code is very clear, clean and well-commented.
Drupal bills itself as 'community plumbing', and that it definitely is. It offers wonderful knowledge management and community functionality. It is not, especially suited to other sorts of sites (ecommerce, brochureware), but the quality of the coding and the very active and helpful user community should make it possible to make Drupal do more or less whatever you like.
A very solid--if specialized--system.