gladmaker : In my over 50 years of driving, I've never had to replace a windshield so I don't know anything about the quality. How can you tell if the quality of replacement glass isn't the same as OEM?
Mainly look at it.
Contrary to popular opinion, aftermarket glass isn't softer than OEM glass, and it isn't fundamentally diferent in any other way, either. All glass, aftermarket or OEM, has to pass the same safety inspections, so the materials and construction are pretty much the same.
The big difference, or potential difference, is appearance. OEMs have very strict appearance and distortion specifications, and they are pretty obsessive about following them. The only real inspector for a piece of aftermarket glass that is being installed in your car is you.
Cosmetic defects are usually pretty insignificant, unless you are completely anal about details. There may be a missing dot in the fade-out pattern, or some of the black may be more grey.
Distortion is the big thing to look out for. Tell the installer that you are going to check for distortion, and will reject a screen if it has too much. Make sure he agrees before you make any commitments. When the glass in installed in the car you should be able to look through it without seeing any significant distortion of what you are looking at. Move your head around as you look through the glass at something with straight lines. You will see some variation in the more curved pillar areas, but a lot of waviness in the middle is bad. Look through a "good" windshield to see what it looks like, then compare.
Other potential issues are scratches, bubbles, or "inside material" which is pieces of debris in the plastic or between the plastic and the glass. Also look for any milkiness around the edges, which is a sign of de-lamination. The is also a phenomenon called "ice flower" that is caused by air bubbles in the plastic growing into weird tree-shaped voids.
You should inspect the glass before it goes into the car. Have them set it up on something so that you can look through it at something approximating the installation angle, and from approximately where you would be sitting to drive the car. Also, check it carefully for the other defects.
You wouldn't accept a badly repaired fender, so don't accept a badly made piece of glass.