The results of the survey will be a very unrealistic sampling of other people's results. What you really want to know is will YOU have a problem.
So, if you are buying a Gen 4, all you need to know is a test fire date of 10/10/11 or later. If you search around, you can find the number for the upgraded ejector (32xxx something). I don't plan to buy a Gen 4 (not approved for sale in California) so I'm not going to search for the part number.
If you are buying a Gen 3 made some time after the SHOT show in 2010, you MIGHT have a problem. Nobody has nailed down the start date for the mods that caused this glitch. It's my understanding that Glock has FINALLY started fixing these guns but don't take my word for it. I don't know if they are actually shipping guns with the fixes incorporated.
AFAIK, these issues are only on 9mm guns. But, again, don't take my word for it. My late model Gen 3 G21SF works fine.
"No matter how cynical you become, it's never enough to keep up." - Lily Tomlin