Concrete5 is an excellent replacement for tired and outdated Joomla websites. Although both are content management systems that can produce the same kinds of websites, the way they approach things (and the terminology used in each) is quite different.
To assist developers with the move from Joomla to concrete5 we thought we'd help out by developing a transition guide. The guide covers a whole range of common tasks and concepts in Joomla and their concrete5 equivalents. This guide has been recently published as part of the official concrete5 documentation.
The guide can be found as part of the 'switch and learn' section of concrete5's official documentation.