Yes, it's anecdotal evidence based on a subgroup of about 20 or so. However, using the same scrutiny this entire board would be invalid. Many years ago, I got a PhD in Music with a minor core in statistics just because I am nerd. While I am aware of a lot of standard principals of statistical analysis, including the ever forgotten B, I do gain knowledge from folks stories. While sometimes I just taking them with a grain of salt, l still realize they have experienced them.
The primary issue that does show up in all of these different discussions is the unwillingness of auto manufactures to share their numbers of failed parts and/or services, heck you can't even get the number of told volume sales.
So, to sum up, I know that on this board probably only once or twice folks complain about the ZF, however the few racing folks (which are mechanically inclined) I have talked with (less than 20) about their "new GM" seems to work in the woes or fears about the transmissions.