For better or worse we have Single Sign On on our Moodle 2.5 install, and most of the time it is positive simplifying and speeding up use for most people. However, the first major issue arrived when LRC staff using a generic LRC log on couldn’t get in to the system. Then we found ourselves having to alternate between manager and admin accounts (see this post for why) and other staff were using generic accounts in classrooms to ease access.
After a little while it became clear that just getting people to set up browser bookmarks wouldn’t really help, so we just set up an HTML block with a basic button linking to http://moodle.yoursite.ac.uk/login/index.php?authldap_skipntlmsso=1. To clean things up properly we also added permissions so that only ‘guests’ had access to it.