Zilch. Or, if I have some, I'm not aware of them (and didn't willingly procure them).
Until some monitor genius figures out how to fixate a permanent focal point on a monitor (right now, even with flat screens, your eyes have no fixed focal point so they continually focus in and out to find one - just one reason people get headaches from long exposure) I will stick with the 2D paper.
Aside warning: I just got back from an entire week, actually 9 days, of computer free living. I logged into a system only once for about 2 hours. I noticed that throughout the week I had as many headaches as I have eBooks: zilch, zero, nada, nil, nul, goosegg, the big nadaroonie. Let's see how long it takes for them to return now that I'm once again poised in front of one.
