Inconsistent illumination on laptop screens

The issues you described are more of a limitation of LCD technology than a design flaw. I also do not believe that the Macs will steal market share solely based on the displays. More and More OEM's are including LED displays with their laptops which eliminates the gradation issue and improves off-axis vewing.

"LED Displays" are simply LCD panels that uses LED backlight instead of traditional CCFL (florescent) backlight. Additionally, that all use edge lighting which increases the chance of backlight bleed along the edges. Backlight bleeding is simply one of the drawbacks of LCD panels.

Viewing angles are basically determined by the panel technology used. Most laptops use TN panel tech which have pretty poor viewing angles, but are relatively inexpensive compared to other panel tech like IPS and VA. Making the panel glossy can slightly improve viewing angles depending on the type glossy coating, but that makes the screen very reflective which can be annoying to people like myself.

My IBM ThinkPad T40 from 2002/2003 exhibits no discernible backlight bleeding.

Yes the laptop screens are LED and some HD LED all have the same uneven illumination, quite poor. I see why they use multi shade backgrounds so the typical user does not notice. Put up a solid color with a classic desktop screen and the color and grey tool bars display uneven color density (ie. dark grey at top lightening to light grey at the bottom of the laptop display. This is very unfortunate.