For the main purpose that they are used for, displays that don't need to be updated frequently, like e-reader or "smart" price tag display.
However updating the display is more costly in terms of power than lcd.
We can also factor in that most e-reader also include backlight.
As a caveat, I appreciate e-ink technology, and the innovation that it brought us. I would also love to get my hand on one of those color e-ink android tablet. But I am not hoping to have a huge difference in battery usage from it, e-reader are very specialized device and can afford optimization that more versatile device cannot.
However updating the display is more costly in terms of power than lcd.
We can also factor in that most e-reader also include backlight.
As a caveat, I appreciate e-ink technology, and the innovation that it brought us. I would also love to get my hand on one of those color e-ink android tablet. But I am not hoping to have a huge difference in battery usage from it, e-reader are very specialized device and can afford optimization that more versatile device cannot.