Upgraders
If you are an experienced Joomla! 1.5 user, this Joomla site will seem very familiar. There are new templates and improved user interfaces, but most functionality is the same. The biggest changes are improved access control (ACL) and nested categories. This release of Joomla has strong continuity with Joomla! 1.7 while adding enhancements.
Professionals
Joomla! 2.5 continues development of the Joomla Framework and CMS as a powerful and flexible way to bring your vision of the web to reality. With the administrator now fully MVC, the ability to control its look and the management of extensions is now complete.