Keys to selling a PMO to executives

While I am not a consultant, we share this common dilemma. I have been tasked with setting up a Program Management Office at my current company. While I have the support of my boss (a VP), other executives and some middle management are not sold.Does anyone have any *specific* examples of how a PMO would (or does) show value to their organization? I have the basics covered: reduce costs, increase efficiency, etc, but I’m sure TechRepublic members can offer case examples of where a PMO *really* proved its merit. Thanks in advance.