I don't understand why we need such ultra-clear screens on a mobile device, it's not a HD TV btw. The iPhone 5's current resolution of 1136 by 640 is enough for me, it's already very clear. As a matter of fact, saw this post the other day regarding retina displays.
Apparently, I don't need anything clearer than a printed page. If Apple's gonna lose any customers because of this, it'll probably be only you.
The human eyes and 300 DPI claim came from the desktop publishing world, where it's generally accepted that ANY image or artwork printed above 300 lines per inch in screen is considered "continuous," as in human eyes can no longer discern the screen dots that make up the image at that resolution. Go grab a print-out from your typical laser printer, and hold it 8-12" away from your eyes, and tell me if you can see ANY of the pixels that make up solid letters. You can't. It is actually generally accepted that human eyes can not discern anything above approximately 240 lines per inch screen when printed and viewed from a normal reading distance, therefore anything above that will be a complete waste.
Since display pixels are capable of generating image in a different way than traditional offset printing screens, it's an easy correlation to make that anything over 240 pixels per inch on a screen will also be impossible to detect as far as the edges of the pixels are concerned. So from a desktop publishing professional's stand point, retina displays are in fact high definition enough to reproduce images that are impossible to detect the edges of pixels just like a high-end printer.
When retina display technology was first defined, it was in fact referring to how the new iPhones and iPads' screens are equivalent or superior to PRINTED pages.
Apparently, I don't need anything clearer than a printed page. If Apple's gonna lose any customers because of this, it'll probably be only you.