What are compelling use cases for having both Chef/Puppet and RightScale/Scalr?

I was wondering about the differences between cloud computing management tools and server configuration software as there seems to be an overlap between them. I would like to have some feedback from customers who have been using both software.

They're actually different products that solve different specific problem classes, but when used together can solve as a system the overall problem of managing a distributed application.

Products like RightScale are good at turning on new machines when needed.

Products like Puppet/Chef/bcfg are good at turning just-turned-on machines into productive members of a distributed computing environment.

Add the two together, and you get a system that can turn on correctly configured and ready to go machines on the fly. You need a configuration management system since some things aren't amenable to burning into an image, or change too quickly for "burn into gold image" to be worth the work. You need the cloud management framework since it's built to be aware of the state of the application in a way that would require a lot of custom-build automation for a configuration management engine.