When you've been asked an unexpected question and are quickly flicking through a document trying to find the relevant section you really do need a faster update than current generation e-ink will offer, something either the iPad or a bundle of printed notes manages.
I'm not saying e-ink won't reach the point where it'd be suitable, I'm sure it will, but it's not there yet and trying to adapt a technology before it's usable for a given situation is a good way to guarantee that it'll quickly be scrapped and unlikely to be reconsidered in future.
Odd. Yesterday when I unplugged my desktop computer from the mouse, keyboard, and monitor and put it in my bag it didn't work at all during the long train journey home.
Suppose the batteries must have been flat.
Any sufficiently advanced technology is indistinguishable from a rigged demo.