http://the-digital-reader.com/2012/1...yes-than-lcds/
After a whole day on the computer also a paper book it not relaxing for the eyes.
There are ambient light conditions where eink devices are much better than tft/retina. I use more often the PW than the Kindle Android app to read books. The default app settings increase the screen brightness so I disabled this setting - with max brightness reading was a pain.