I think part of it for me is also the idea that something on a computer screen (or computer-type screen in the case of another LCD-based device) is not as... real. Aside from the eye thing, I just find it harder to mentally focus on the stuff, a problem I don't have with the printed page. I don't know if it's the mutability of most computer-based data or the distractions I'm used to having on such devices, but... There's something there that I haven't found a way to completely overcome yet.