LCD Question - Odd diagonal gradient or uneven lighting

I have been in contact with support for some time now. Long story short, my original screen on my Inspiron 9100 had some defects and I thought I'd have them fix it under warranty. They sent me 3 LCD panels and I installed each one and each time they were refurbished LCD screens and all had problems greater than that of my original screen! So finally I sent the whole laptop in and they replaced the screen with LCD #4. I got it back and this screen is very close to good but still not quite up to snuff.

It has what many of the others had... A strange diagonal gradient when you look at a black or dark screen. It's hard to describe. It looks like uneven backlighting but I don't think that is it. It is always brighter in the lower right corner and darker in the upper left corner. If I watch a dark movie scene, for example, and I move my head just to the right of dead center, the upper left corner looks kind of inverted. But if I move my head the other way I don't get that same effect. Needless to say it's a bit annoying.

I am having troubles researching this strange phenomena and I don't know what to call it. It's hard enough to explain. My original screen was very even and I could look at it from side to side horizontally both ways at reasonable angles without this issue. One of the screens Dell sent me did not have this problem and was very evenly lit and symmetrical but had issues with dead pixels. I feel like I can't win. :-/

Here's a picture of one of the screens with this problem:
http://ip.gliebetronics.com:800/dell/After_with_black_full_screen.JPG

Does anybody have any technical explanation as to what this is? Any ideas on how to get around to getting a nice even screen again? Or am I being way too unrealistic? You'd think that a $600 LCD screen would be of higher quality.

Thanks in advance.
-Dan