Joomla! recently released 1.5 Beta-2 version of the popular open source CMS. It is a completely re-factored code written from scratch (160 K lines of code) and finally does away with the Mambo code base. In a way it represents what Mambo would have been if the split had not happened.
However, don’t rush to upgrade *yet* because if you have been using an extension that was developed for Mambo, it will most likely not run on new Joomla! any more.
Here’s my take on the CMS Watch post.