Originally Posted by Synamon
Since I hold my reading material more than 20" away from my eyes (I was curious so I got out a tape measure) anything with 160+ ppi is retina for me. Heck, my 130 ppi laptop is retina too, since the screen is more than 2 feet from my eyes. 326 ppi sounds impressive, but it only matters if you want to squint at your phone a few inches from your nose.
Interesting. I had to get a measuring tape out as well, and when I'm reading comics and magazines, I hold the iPad roughly 12-14 inches away from my face.
I certainly saw a huge difference going from the iPad (1) to new iPad (3), which fits with the table you gave.