I have 2 setups, both for non-profits. One is an annual event where the event coordinators need to be able to share documents, post images of the event, and basically manage a website. That one is currently using a Wordpress installation along with Google Non-profits.
The second is a PTA association. This one is coming on board now and they want a small community (profiles, image sharing, document sharing, calendar, RSVP functionality and the ability to have members-only content). I don't think Wordpress is a great fit for this one, hence the reason to look. My wife likes Joomla for that one so far (she manages both of these websites).
Another thing holding me back is the ability for my wife to design the template for the site, which she is currently doing in Artisteer and they only support a handful of CMS packages (Wordpress, Joomla, Drupal, dotnetnuke, Blogger). I'm willing to figure out something for another CMS if there is a better one so that's not the a huge blocker.
Does that help?