At RPM we use RPM

In our industry it's called "eating your own dog food". RPM is our CRM. All RPM sales opportunities are managed through RPM. RPM is also our project management (installation), support management, and trouble ticket system. We use every new version ourselves before we deploy it to everyone else. We tried other tools before including Microsoft CRM, but RPM has worked out much better for us (of course we'd say that).