...but you almost never hear from people who aren't having issues and those of us who aren't having any problems...
You also don't hear from people who don't post on forums or don't subscribe to MacRumors for any number of reasons, which I am sure is a far greater number of MacBook Pro owners than those who do post. While we have no idea what percentage of those who don't post are having issues and don't come here to post about it, I think it can be argued that it is a two-way street.
I think the number of people who have had at least one model with a keyboard failure and those who have had 3, 4, 5, 6 models in a row with keyboard failures, coupled with in-store display models that have exhibited keyboard problems, would suggest the number is higher than 5%.
I heartily agree with you that it isn't over 50%, but I would likewise be shocked if anyone could show evidence that it is at 5% or lower.