wordpress MU

Hi to all, have you upgraded your Wordpress site to the latest version 3.1 or the they called the Worpress MU. Wordpress MU (Multi User) allow the administrator to setup sub-domain and sub-folder for its site. Furthermore you can add user for every sub-blog/sub-domain/sub-folder that you created. Wordpress 3.1 has the SUPER ADMIN access that can set all the functionality for its sub-domains and