I have intermittent issues with some books that download and immediately disappear from the HD+ and/or the reader will not open and the content wants to download again. Since some of my content is still not compatible with my NookColor I haven't deregistered it yet. From the Nook Color I can usually download and open the book that won't download on the Nook HD+ so I know its not entirely the book itself. After multiple downloads of a book or content - so far the book will finally stick and can be opened on the Nook HD+.
I am also using my NookColor to Archive books and apps as "sending to the cloud" via the HD+ doesn't remove the item from view like archiving via NookColor. The HD+ can view the archive so that is good enough for me.
Now if some of the app developers would just update their apps like Scrabble and Prince of Persia!