some of you are missing a very important aspect.
the 326 pixels per inch that Apple use in their retina display ARE noticable if you are viewing from a distance less than 12 inches (if you have good eyes). Take a look yourself up close.
12 inches and beyond the human eye cannot detect the pixels. Mr Jobs even said this himself at WWDC.
if you actually think you cannot detect the pixels because Apple say so then im afriad the education system has failed YOU.
a higher pixel count IS beneficial if you are viewing from a closer distance, as the edges will appear smooth throughout the image.