there can be some quality control issues, but not a huge problem if you buy them from a luxottica-owned retailer.
i had a pair a few years ago (of an unfortunately discontinued style) where the lenses began to come away from the frame (not popping out, but on their way to doing so). went back to the retailer (sunglass hut) and got a replacement no questions asked. same thing began happening to the next pair. got another replacement. those were solid, but unforunately were lost. at that point the style had been discontinued.
would happily buy another pair if i could find one that suited me, though. the quality of the glass lenses is absolutely fantastic compared to other brands--everything looks better/sharper--particularly given how many have resorted to polycarbonate. the glass lenses also tend to be more scratch-resistant than polycarbonate, obviously.