The top use case I can see (and have used) is setting up kiosk systems for temporary installs of non-networked (when deployed, isolated when being configured), non-sensitive exhibits. I would never trust it with free reign of my personal computer, but helping me get the environment set up for something I'm throwing away after a week saves me a lot of time with minimal risk. Step 1 is always determining the risk of your activity and the threshold of risk you're willing to accept for a given task.