I read Lights Out as a .pdf on my desktop pc a few months back and it killed my eyes. It was terrible and I work on my laptop for work a couple hours a day.

The e-ink format is much easier on the eyes. Eye fatigue is really a non-issue in this case. There is no backlight or harsh screen glare. The background is a brownish grey like a paperback book. I spent quit a bit of time reading from Kindle, Sony, Nook and none of them caused me any eye strain or distraction.

The true debate on these should be on battery power. IIRC all those I mention will last several days on a charge. I know the Nook is rated to last about ten days with wifi turned off.

When comparing to tablets, remember these will be essentially netbooks/notebooks or in the case of the Apple Tablet a giant iTouch. Those batteries are judged on hours of charge, not days.