I'm reminded of the problems Sky and Tivo had selling devices in the early days of PVRs. It's really difficult to explain how good and useful they are without sitting someone down with a real one and showing them. I bought my parents Sky+ a few years ago. My mum was opposed to the idea. She had a perfectly good video recorder. Why would she need this thing? Try and take her PVR away now and she'd gut you like a hog.
I think Ebook readers are going to have the same problem. Some people are in full on "Art beard" mode and think there's something magical about holding bound paper in their hands (Shouldn't the story be the important thing?) and others aren't aware of just how good e-ink displays are for reading text.
It might change somewhat once more branches of Waterstones get demo models in. It'll certainly change once the price of the readers start dropping more.