Good point, it has many of the same advantages: low power, sunlight readability. Why isn't it used more often? The OLPC had a dual LCD/LED display (PixelQi) and it worked very well.
RLCD is starting to pick up in some niches in China (e.g., the Hisense Q5). Its main disadvantage is that it tends to have a color cast depending on the nature of the ambient light, which e-ink doesn't, but it is cheaper and has higher refresh rates.
