Some observations, from my limited number of patches/bug reports on CPAN:

1. modules that are heavily used tend to have fairly good turn-around on bug reports & patches (which may just be because heavily used modules have more patches and bug reports). Case in point: DBD::mysql still has some outstanding unicode bugs, but AFAICT that's mostly because nobody can figure out a good way to solve them, and there is at least some discussion on the RT about them. (Note that DBD::mysql also gets a lot of "bogus" bug reports due to its not very robust test suite). The patches I submitted were incorporated in the next release (which took about a month and a half IIRC).

2. Some modules really only have a few users, and the author might have moved on. Authors of those modules (myself included) may not be very actively maintaining them. I try to keep Audio::LADSPA more or less up to date with bugs, but it can take a week or two before I can work up the energy to check out a patch or bug report on it. My schedule is pretty hectic at the moment and I can't really afford to spend a lot of time working on stuff that isn't directly related to my job during the day.