I have an astigmatism and I know from experience that with an uncorrected astigmatism, reading anything for an extended period will cause eye strain, paper, eink, LCD, CRT, or smoke signals in the sky.
Even paper print has a variety of quality levels. Look at the difference between a glossy magazine and a cheap paperback (especially one from the 1950's). If you look at my reading devices you'll notice quite a variety (mainly because I'm a gadget freak). There are times and situations when each of my devices hold superiority over all the rest but none holds superiority in all situations.
I'm retired now and read a great deal. With eink, my eyes begin to tear a lot toward the end of the day. Ereaders of any (quality) type are better for me because I can adjust the font size for the light conditions and how tired my eyes are.
I love my NC. I also love my Astek EZ Reader (an eink device) with OpeninkPot firmware. Sometimes I read on my PDA or my Droid (partly because of the back light but mostly because they fit better in my pocket and therefore travel better. (I've decided to not carry a purse because my wife would laugh at me.
) For me these two ereaders (with either my PDA or Droid) make the best ereader.
One great reason for the NC though is that when rooted it also functions as a pretty good tablet PC (and will get me by until my real tablet PC - a Notion Ink Adam - gets here, at which time I'll have yet another gadget --- ain't technology great -- but costly).
For me, one reason that LCDs cause eye strain is when the brightness is set too high. I read my NC with its brightness set very low and with the night mode on. So far it seems to cause less eye strain (for me) than the eink display unless I try to read it in bright sunlight.
So bottom line, we each should find the best solution (as we each determine what best is) for ourselves. I'm just glad there are so many people here who can help us in finding data for making that decision.