A good look at the Alpha2 version of Joomla 1.6. Joomla is doing a great job of explaining new features, including new SEO features  they've taken on board of a lot ability to control the metadata for each page. The first step towards a full featured ACL (Access Control List) has been pushed into the development branch of what is to become Joomla! 1.6. The other side of ACL is granting permissions to users to take actions on objects.

Here again there is a big change between Version 1.5 and 1.6. Each object in the front end can assigned an Access Level. The Special Access Level includes the Administrator, Manager, Publisher, Editor, Author, and Super Users groups.

Here are the overview of ACL on Joomla 1.6

Resource : http://docs.joomla.org/ACL_Tutorial_for_Joomla_1.6