Well, another one probably heading towards the Drupal world...
I've been running a car club site on PostNuke for a bit over five years, so I'm very familiar with their way of doing things. PostNuke has upgraded to Zikula, and - whilst it's a good CMS - there's a few of the add-in modules which I've been relying on which don't seem to be alive any more. The pace of development has dropped off, and I'm starting to wonder if the version upgrade is worth it, or if I'd be better pushing my effort into a move to another CMS.
I know you lot are just a bit biased, so you won't disagree when I say that Drupal seems to be the platform of choice.
The basic structure of the site is that unregistered users get access to a lot of the content, but registered users get a little more. If a registered user is one of the c.2500 current paid members of the club (this is a mainly offline club, with real-world events and meetings, and a monthly dead-tree-edition magazine), then they get access to everything - they tell us their username via a form, allowing us to manually tie the two together behind the scenes, with access controlled by physically adding the user to or removing them from a group.
Having a first look around Drupal, I'm seeing that most things I'm doing now have direct equivalents, and migration looks relatively straightforward for most.