[Myztiq]

Runnable engineer here, let me see if I can clarify some things.

The core use-case is being able to manage and test feature branches. In particular, some of the tricky things with pull requests related to integration testing.

Each feature branch can have it's own isolated environment for testing, pointing to different branches for other parts of the stack. This makes it so you no longer need to manage your staging servers, deal with outdated components on the server or even have to wait to be able to test your code. It's always there, always up to date and unique per branch.