The most useful feature is that you can make sure your application will not crash if it encounters an exception, so there's no need to worry about writing try-catch blocks everywhere in code (which would be very tedious). It also allows us to track all exceptions our users encounter with their apps - which helps identify issues quickly when they occur. I dislike how difficult it can sometimes become to find errors once they're fixed by this tool; we've had many problems where bugs were found months after being reported but never resolved because of lack of visibility into what was going wrong internally at one true error. We use one truerror as part of our development process to ensure everything works correctly before deploying any changes or new features.