I agree with this completely. Since I starting forcing myself to over comment my code, my bebugging cycles have gotten much shorter. Not only does it mean less bugs get out the door, but it means if something is too ugly to admit I'm doing it that way, I can't just pretend it's not there; I have to admit it sucks, or do it right.
Also, it helps to _find_ bugs. Something may be obvious, but that doesn't mean a person should have to parse it all to find the stop they're looking for.
And since we all improve over time, what was obvious when I wrote the function might not be obvious at all when I'm debugging it. More like, "did I really do that?"