Is it possible to have one account have full access rights to all mailboxes.........the equivalent of 5.5 service account rights. I know there is a one liner for individual permissions......can this be done with the GUI ? thanks

Are we talking about Exchange 2003? http://support.microsoft.com/kb/821897/en-us

apologies I meant to say for Exch 2007.Actually found already that the only way is through the EMS

Just to amplify: you can use the add-MailboxPermission task in EMS to do this for one or all mailboxes. You can also use add-ADPermission to change permissions on AD-based objects, which is useful for delegation.