I imagine you have never seen one then? The backlight on the paperwhite is actually a frontlight, so it doesn't strain the eyes, I find it a lot better than any old Kindle, or frankly - than reading an actual book.

Why should it matter for eye strain whether it is a frontlight or a backlight? In both cases, it is some amount of light reaching your eyes. What should matter would be just the brightness/contrast and uniformity of it.

In my eyes, it's called the "paperwhite" because when the light is on, the page is much closer to white than the unlit Kindles, which have more of a grey background. Not because the background is #FFFFFF and the brightness of the sun.

It's quite readable, not quite pure white actually. Contrast is very much like reading newsprint, and the lighting is also easy on the eyes.

this is only a data point, but I own a kindle 3 and a paperwhite, and I used to read on my iPhone before that.

The paperwhite is amazingly readable, and not at all comparable to a computer screen white.