Interesting but not really useful.
Screens are the weakest and most expensive part of ebook readers. I recently broke my cybook screen and it's not worth it to repair it. I'm buying a new one.
Dual screens mean at least double the cost and make the device unnecessarily complex , bulky, (and breakable).
IMHO a dual screen offers no advantage over a good window manager.
Interface advantages such as natural flips will be easily replicated with flex displays, which will finally allow up to A4 sizes without sacrificing mobility.