[fdkz]

A lot of people will be able to tell the difference. For example I routinely try to read pdf books on my iphone 4 ibooks (without zoom), but it's hard because there are not enough pixels!

http://www.displaymate.com/iPad_ShootOut_1.htm

.. Apple’s definition of a “Retina Display” is actually for 20/20 Vision (defined as 1 arc-minute visual acuity). However, 20/20 Vision is just the legal definition of “Normal Vision,” which is at the lower end of true normal vision. There are in fact lots of people with much better than 20/20 Vision, and for almost everyone visual acuity is actually limited by blurring due to imperfections of the lens in the eye. The best human vision is about 20/10 Vision, twice as good as 20/20 Vision, and that is what corresponds to the true acuity of the Retina. So to be an actual “True Retina Display” a screen needs at least 573 ppi at 12 inches viewing distance or 458 ppi at 15 inches. The 326 ppi iPhone 4 is a 20/20 Vision display if it is viewed from 10.5 inches or more. ..

[ugh]

Apple doesn't do that kind of stuff. Most people will not be able to see the pixels (at their comfortable viewing distances). That’s good enough for them (also considering they are streets ahead of everyone else in the pixels department).

[tedmiston]

It's a marketing term. That's just being pedantic.