Technically ereader screens are frontlit: the glass in front of the e-ink display refracts light across the display evenly. So instead of looking right at a light source, you're viewing refracted light scattered across the entire display.

I also get a headache from backlit screens. Frontlit e-ink is much better.

The Kindle Paperwhite uses flattened fiber optics to bounce the light from the edges off of the epaper, so it is still more like indirect lighting than reading on a phone. In a darkened room, or when I am reading outside at night, it works pretty well. When I'm on a plane, or when I'm in a resturant, I don't have to fiddle with an external lighting device to read.