Since Joomla! was released back in 2005, the geeks here at 3B have been in amongst the founders helping to suggest tweaks and improvements to the benefit of our clients.
Joomla 1 now seems like an age ago, and even though we still have some fond Joomla 2 memories, we are absolutely on board with Joomla 3.
Our Joomla websites
The two are reasonably representative examples of the sort of organisations for which Joomla is appropriate. Squarespace is simpler, and Drupal is more powerful, yet Joomla sits somewhere in between as an ideal CMS for schools, member sites, and associations.