The recent split of Mambo development has been covered in many places, including Slashdot. While reading the comments, I came across this post from someone who develops for Mambo. http://developers.slashdot.org/comments.pl?sid=159398&cid=13350391 His gripe is that backwards compatibility breaks so often between releases that modules become obsolete and unusable. This renders Mambo useless as an application, but makes it useful as a framework for user authentication and session management. Compare this with what we sometimes break (the most recent example in my mind is the statistics module which removed the capability of tracking hosts, which quickly told me what pages a user have visited and what referers, among other things in statistics). There are lessons here to be learned I am sure.