I am keen on a two page device - I think having two pages on view is an important part of how normal paper book reading works. We do a lot of "reading ahead" without realising it - not reading the words, but the layout, the approach of new chapters, paragraphs, etc.
It's also nice just to be able to see more of the text without doing a lot of page flipping.
Having said that I'm not so keen on the design of this prototype. The screen frames and the hinge look huge and obtrusive.