We are a partner with CA Technologies, and we've done major implementations of Clarity for around 40 to 50 different customers of various sizes. Some are small, while others have a massive infrastructure running multiple instances of the CA Service Desk. It's deployed exclusively on-premises, and that's one of the reasons CA is losing market share: It doesn't offer a cloud solution.
Our customers implement Clarity for incident, change, process, configuration, and problem management. The service catalog is another popular feature they use. Clarity offers process automation as well. You can make multiple dynamic workflows to compile or integrate those processes.