The question I'd like to raise is one of practicality. No one system is able to do everything, and certainly Joomla isn't invincible.
I've found that it has trouble with fine control of users, with a very hard to modify permissions system. There are extensions, yet they pretty much build from the native user system.
The system is not very well designed to provide portal systems, so it doesn't do well with providing a unique experience for each user once they login.
One of my original ideas for looking into CMS systems was for group-collaboration needs. Joomla again does not provide these features natively, and I don't know of any good extensions to manage these kinds of tasks.
What have you found to be difficult or down right impossible with Joomla?
One of my minor issues with Joomla is that in order to add new static pages & menu items you must log into the backend. It would be wonderful if Joomla had the ability to hacve a user control panel for the frontend users (publishers +) to add pages, remove pages, and manage menus....
Hey Phillip! Thanks for the links! I'd seen those before, but never tried them. The axtaweb one is very nice, but it doesn't allow static content creation