I read most of my e fiction on my eBookwise 1150, with the backlighting turned way down, and I find it more comfortable than reading on my Powerbook, but that's probably largely due to the form factor. Reading on an LCD screen doesn't bother me, and I do it all day for work. It's just easier to get comfortable with the smaller eBw 1150. But I also like to read in sunny environments (in warm weather) and I can't do that on the Powerbook, whereas the eBw 1150 handles sunlight just fine. If you only read at night, I guess a backlit reader or tablet is the way to go. I just like to be able to go outside.
Regarding health, there doesn't have to be a study showing a health issue to justify someone not being comfortable reading on LCD. If it hurts, don't do it. Some people don't like the flavor of asparagus, either.