What are some real world examples of SUCCESSFUL configuration management system implementations in large, complex environments?

I have read several case studies on configuration management implementations and all indicate that only about  15% of companies attempting to implement a CMDB have been successful.  That's an abysmal percentage for a project that is both expensive and time consuming and therefore unlikely to gain much traction with IT leadership.  Can anyone provide real world examples of a system being implemented in a large, IT environment hosting a variety of technologies and supporting many different business units?  I have also read numerous articles from Forrester and Gartner and had conversations with consultants from the large consultant shops but they only speak in generalizations.  I'm really looking for real world examples of succssful implementation backed with true analysis of benefits realization and cost vs. benefit.  Any info you could provide would be greatly appreciated!