I set up the system administrator user during the setup wizard - it asked for a name so I chose "administrator", because we want a separate email account named "admin". That account is listed as the primary administrator for the server: http://screencast.com/t/XpTNskDkyx1
When I log in using "admin@calebnetwork.org" I get the standard user interface.
When I log in using "administrator", with no domain, I also get the standard user interface: http://screencast.com/t/ew72qd7Wp