I just read an article in a local computer magazine about why digital books, magazines, ... don't do well. As an example the author showed a case with Steven King when he tried to publish one of his books only in digital form and failed. He concludes that the problem is that each customer can get a digital form of the magazine easy and even not pay for it and he puts his hopes in an efficient methods to secure digital copyrighted work. Hmm... why do I smell DRM here ? I think that now more and more music record labels recognize that DRM is evil. :))
My opinion is that there are NO devices that would have properties of regular paper. I refuse to look at PDFs(for example) on LCDs or some other semi-appropriate device for reading them. I'd like to have a light device, that is nondestructable and easy to handle, like paper is. :)))
Maybe technologies like E-Ink, Digital ink and others will bring the ease of use.