Originally Posted by Shinobi-X

The windshield is actually a bit more critical than that. It functions as both an effective safety item and adds structural rigidity to the frame/roof of the car. OEM, in this respect, is great...but in order to be sold in the US, reputable non-OEM supplied glass from any of the big makes, must also meet the same safety standards. OEM, however, gets marked up mainly because of the Lexus stamp on it.

If you think about it, OEM windshields are mass produced in large volume, to also include replacement parts, which typically drives costs down...and yet, they are exceptionally more expensive than quality windshields made by various OEM makes, who also produce OEM glass for various Toyota/Lexus models, among other brands. For the non-OEM suppliers, they are typically in competition with each other, and so they are forced to offer competitive pricing to not only the marked-up OEM, but also each other. In the case of the IS, they weren't contracted to do the work, and so there is no Lexus badge that can be used as leverage to mark up the price.

There is certainly bad glass out there, but of the manufacturers which sell in the US, the windshields code can be checked for just who its coming from. In a nutshell, the OEM supplier is great and will/should always be recommended, but so are the reputable OEM aftermarket makes, such as the aformentioned PPG. Past that, a bad installer is the thing to watch for, as the vast majority of problems occur with the quality of work/materials.