The kernel bugzilla has certainly worked quite well for me. I've filed
and had fixed several -rc bugs that nobody else seemed to be running
into, that may well have made it into the full release were it not for my
report... which might not have been filed had I to try to figure out the
proper mail interface and rules. At least bugzilla is reasonably
familiar for those who run testing and early releases and regularly file
bugs elsewhere, thus already knowing a bit about the process, hopefully
therefore filing better bugs as a result.
Kernel bugzilla therefore expands the feedback loop, opening it to people
whose testing and bug reporting otherwise wouldn't be heard. When the
object is a stable kernel release and the testers are all volunteers,
that's a GOOD thing. =:^)