I may not have been clear in some things that I said.
When I said that you can't download Nook books from B&N now, I did not mean from B&N to a Nook reader or some other proprietary B&N device or program. I meant that you can't download your ebooks to your computer in order to back them up.
And, actually, that is technically not true (it seems that someone else mentioned that in this thread). The best, and most detailed information, that I have seen, about how you can do it (though with difficulty) is
here. That is a post on a blog (a very good one, IMHO) maintained by our "own" Koland, who frequently posts here and there on MobileRead.