So far, we have talked about categorizing PRs by what part of the system that they involve. However, only developers and expert users tend to think in those terms. Most users tend to think in terms of "symptoms".
The task: to map a symptom to a specific part of the system.
Commonly submitted "symptom" PRs, and what they might map to:
Cannot install or boot FreeBSD
Cannot get xyz to work
Panic or hang under certain conditions (e.g. stability/uptime)
Regression seen after updating (should be easy to isolate and assign)