well i see pixels on my 5s. and that is ~320 ppi. i think that they could do better on a phone, i can certainly see pixels.
for a monitor, it depends how close you sit to it. but 220 ppi seems pretty safe. at least it works for my 220 ppi 15 mbpr. and my current monitor sits about as close to my face as my laptop does.
so i think they should increase the resolution on phones/tablets, but for laptops and desktops ~220ppi seems good. certainly not excessive
Edited by perfectblade - 10/17/14 at 9:23pm