In the spring of 2009 Sun Microsystems went live with their implementation of OBIEE and presented at the North California Oracle Applications User Group. The original document is found here,
but I have also mirrored the file here,
The document highlights some of the benefits of bringing OBIEE into the organization along with pros and cons and usage of the BI Meta Data Repository. At a minimum there are some great bullet-points here that could be leveraged for your next OBIEE presentation.