Regarding the Nook. When I talked to a B&N person about the Nook about 6 months ago, they said that there was no limits on the number of Nooks that could use the same password. They might have been mistaken though. You would need to register the reader with Adobe to use the Adept DRM though.
And alas, yes, the DRM issue with ePub is a mess. Many of us support ePub, not because we feel it is superior to Kindle DRM, but because at least the format itself is open, and we very much believe it would be a bad thing if the Kindle became the only device out there.
In practice, if you bought a Kobo or Sony reader, and bought from their book stores (for either device), once everything was set it should be as seamless as Amazon for loading books. Though, since I don't buy DRM books, I wouldn't know
.
--
Bill