If you're like me, rule tracing used to be this arcane thing support would make you generate for really hard problem, and the output was a rather unwieldy xml file that made you want to stab your eyes out, but would ultimately tell you things logging wouldn't.
I have good news:
For those who weren't at FOCUS, there's a new feature that managed to be unknown to me until Sven presented it at the web gateway user session last week.
It's documented with screenshots here
If you feel the need to hug someone after you see this and use if for the first time, I've got you covered (I hugged Sven after his presentation).