The term "retina" is just marketing. I can see the pixels on my ~300ppi phone at "normal" distance... and the very smallest fonts it uses (in mass dictionary l

The term "retina" is just marketing. I can see the pixels on my ~300ppi phone at "normal" distance... and the very smallest fonts it uses (in mass dictionary lookups) are so small that there's still discernible shape distortion in complicated kanji. This only really affects usability in a few cases—distinguishing between very similar, extremely complicated, kanji, in an unusually small font used for a specialized application—but these cases do occur. There's also some room for improvement in font-rendering of Japanese at the somewhat larger sizes used for displaying email or such, where they're still using hand-tuned fonts even on ~300ppi displays. So at least in Japan, a 440ppi display could be put to good use. [And really, even once pixels are truly not individually discernible, higher resolutions can still be useful. For instance, although text printed on a 600dpi laser printer is usually very readable, it doesn't look so good when compared to something typeset at 1200/2400/etc dpi...]