Perhaps I can help a little. I have read a lot on the Dell i9200 and XPs problem and the Sony screen. As far as I can discern there are currently 4 types and 3 manufacturers that make a 17" WUXGA screen.
In my knowledge, sony has always been a manufacturer of its own screens. This is based on CRt technology however, and could be wrong. but i'm willing to bet the sony screen is also made by sony. Since it would be a difficult screen to make, with such high quality, they might not have enough factory resources to make them for other OEM's as well. Otherwise what Adam suggest, that the manufacturer of the Sony screen has an exclusive contract with sony that is not about to end, pretty much results in the same thing.
There is light at the end of the tunnel though!
The 'dell screen' can actually be one of three screens. The screen model name changes around often at dell, but people have been able to discern three different types of LCD panels. Only one of these, the LG Philips one, is usually rather horrible. It seems to be a matte screen that is glossed over(how STUPID can you be). Hence the logical 'sparkle' effect that ruins the screen. Light leaking is also a problem, but not always present.
The other screen, which is what you will get if you send your i9300 back or request a replacement screen, is actually a Samsung screen. This screen is supposed to have none to negligable sparkle, and a better brightness. The Samsung screen seems to have less vivid color, but this can be easily solved by adjusting the standard gamma at which it is set.
There are two Samsung models that are used in the Dell's. If anyone really cares I can look them up. I can remember now that the one with the lower model number was supposed to yield better results.
If Sager is testing the WUXGA screen of LG, it is no surprise it didn't meet their standards, and it proves they are committed to quality, unlike the box-shovers at Dell. However I urge Sager to perhaps try the better Samsung variant.