Presumably, it would also work to just plug the Cybook in and "top up" the charge before it ran down completely?
At any rate, since this will at least sort of work, while it's a given that neither the Mobipocket nor the Adobe files from Overdrive will work with the Sony Reader at all, it's enough to finally push me into going with the Cybook. I've ordered the Cybook Deluxe through Bookeen as of a few minutes ago (since the NAEB offering is apparently still in limbo) - let the countdown begin.