It's a bit strange that, as system administrators, we have bullet-proof tools for fault management and performance monitoring (the latter at least if you work with a black-box model for a system, performance tracking at transaction level is an entirely different beast) and on the configuration management side we are at the very beginning of a widespread adoption of these or other tools.
I think that configuration management is not something you need when you have thousands of maybe almost identical servers, but an essential foundation for your infrastructure; especially because you can describe a good part of a system administrator's work as "something that changes the configuration of a system", so managing the configuration will help a lot in managing, staffing and evaluating system administrators.