Wow, thanks for your quick answer !
Rather want than need... I'm a graphic designer, illustrator and like to sketch, jot down short novel ideas, collect pictures... Really a multitasker. I kind of anticipated the dual screen trend that could have emerged from the microsoft courier (http://www.youtube.com/watch?v=GlpftPSuXe4
)... obviously it just won't happen soon, if ever
I'd use it to work as well as a digital artwork in itself : a unique interactive book-like device is an artistic argument...
I see Chalkboard Electronics is to release 7" capacitive screens soon which might interest me if I could get the USB equivalent for the other "page".
btw this page on the wiki has some DSI related information, maybe not enough to get a grocery list out of it...
Is there somewhere where I could find more details (DSI placement on the Pi board, known-to-work displays...) ?