Both my iPad mini Retina and Nexus 7.2 are great for reading on as far as clear screen, good lighting, dark and sharp text. I never see the battery as an issue since they can only be read indoors and it is easy and convenient to keep them charged. But the catch is that they are heavier and bulkier than eInk readers, and forget about using them outdoors during the daytime. I almost said they are more expensive too, but the Nexus 7.2 and Kindle Voyage are both $200 USD.

The screen ratios are different on most Android tablets I've seen as they tend to have a 16x10 or 16x9 ratio and are really designed for landscape use. The Kindles have always had 4x3 in landscape but have been designed for 3x4 portrait use. The iPads are 3x4 as well. The narrower and more elongated 16x10 is okay on a 7 inch tablet, but it is too narrow on a 4" smartphone screen.

Most of my reading in the past year has been on LCD devices: Mostly my iPad mini Retina. But it would be nice to have the versatility of an eInk reader to compliment the tablets, especially for outdoors and traveling.