Note that the whole point of the "retina" branding is that at a certain distance you will no longer see any improvement as you move further back. If those people were standing sufficiently far back (as you might when looking at a store display iPad) then the retina effect will kick in.

The difference between the retina and non-retina products is shocking once you're accustomed to the retina version.

If I pick up my wife's iPad 1 or my old iPod touch, it's like looking at a jumbotron. It's the first thing I see. "Ohh, a big clunky grid of pixels... I forgot!"

For now I haven't switched my computer screen, but I worry after a few weeks on a retina monitor, I'll have the same reaction to other displays.