I first saw this E Ink technology at the end of the last century and thought it had a “wow” factor even back then. If I recall correctly the first use was for electronic signage since the displays only required power to change the display. Once the E Ink pixels are set on the page, they stay readable without need for power.
I've been looking forward to electronic paper though. Just think: a single E Ink page attached to a “spine” that contains the book files. At the touch of a button on the spine the old page goes and is replaced by the new page. When you’re finished reading you simply roll up the display around the spine and put it in your pocket.
The first eBook readers using E Ink (from Sony and iRex) aren’t flexible at all. I gather that manufacturing the flexible polymer displays is tricky but the good news is that someone is working on it.
L.G. Philips LCD have just announced that they have developed the world’s first 14.1-inch flexible color E-paper display on metal foil. Samsung and Primeview International recently showed a plastic version.