It's really a pleasure to view high pixel density displays (measured in Pixels Per Inch, which is different than overall pixel count). The other component is color range (gradations of shades). It's like the difference between listening to raspy low-definition speakers and high quality speakers that carry all the detail with truer fidelity. Just easier on your senses.

BTW -- For you Windows users: I switched a few months ago to a Microsoft Surface 3 Pro and it has similar density to Apple's "Retina" displays. (216 PPPI vs. 220 PPI for the Retina MacBook). It's really a pleasure to use -- font renderings are smooth like typeset print -- and everything else is so clear.