When beta-testng software, it's just as important to know what environments it's working in as it is to know what ones are causing failures.
Also, it can be quite depressing for a software author to never get any positive feedback and always get only negative feedback.
Similarly, for beta testers, it's useful when tracking down bugs to know what features are known to work.
The report that I'm planning to provide contains much more information than just "it works." Providing more than that simple example didn't seem appropriate while composing my question.