I've found this to depend more on the project and leaders than open-source vs. proprietary status. For example, I've been quite happy with the responses I've gotten to bugs submitted to Debian, some of which have been fixed on the same day--- which has never happened when I've reported bugs to any other operating-system vendor. With most of the commercial software I use (Microsoft, Adobe, Apple, etc.), I'm lucky if it's at all possible to reach anybody and get a response, much less a fix, even with a quite specific, reproducible test case. Heck, even GNU Octave's team, while understaffed, is more responsive than Matlab's, and we pay some mega-$$$ for a Matlab site license.