Some years ago Elke Greifeneder and I offered a seminar in which students tested their reading experiences on a Sony eBook reader, a laptop, a desktop computer, printouts, and a bound book. The reading content consisted of German novels and the students measured the experience only by testing reading speed. The result was that there was no apparent difference between the eBook reader and other media. The students subsequently published the research (see Grzsechik, K. et al, (2010), "Reading in 2110 – reading behavior and reading devices:a case study" The Electronic Library, Vol. 29 Iss: 3, pp.288 - 302 or online at Emerald).
Now a more extensive study at the University of Mainz has reached similar conclusions: "Almost all participants stated that reading from paper was more comfortable than from an e-ink reader despite the fact that the study actually showed that there was no difference in terms of reading performance between reading from paper and from an e-ink reader." The study also found that "the older participants exhibited faster reading times when using the tablet PC." (Source)
The general assumption in Germany is that a strong cultural preference for print on paper is likely to persist. It may, of course, but if the US experience offers any indication, the resistance may give way to the convenience of having multiple works on a single device. On my iPhone right now I have a dissertation and 4 novels. The iPhone is a bit small for dissertation reading, but I never read scholarly works on paper any longer because I want to be able to search them and to look up references simultaneously. I also buy fewer and fewer novels in paper form because I do not want to have to carry one more object with me.
A few years ago I thought that an interesting study would be to sit in the Berlin S-Bahn (elevated train) and count the number of people using eReader devices. Now such a study would be harder, because such a large number of people spend their transit time doing something on their smart phones, but whether that is reading, playing games, or sending email is hard to say. Or perhaps what they are doing is irrelevant. Whatever they are doing, it seems to involve reading on an electronic device.