Re: @ Gribbler
I also prefer e-ink to the illuminated lcd. But, I suspect the comfort is due to the brightness/contrast in each reading situation. With e-ink, it's much like paper; only reflecting back ambient light from your surroundings. Too dark to read? Turn on the nightstand lamp and still, contrast is not high because e-ink is no brighter than the environment illuminated by the lamp.
With lcd, it's pumping out bright light right into your face. Even on lowest brightness settings, most devices are still way brighter than a dark room. That contrast is fatiguing. Reading from an lcd in a day lit living room doesn't bother me that much. Screen refresh/flicker might also get people, but as the lighting technology is not CRT, I wouldn't put much weight here.