Nook for Mac now has shelves, so I'm happy about that.
Next step, I hope, is for shelves to be maintained across environments. One set of shelves for my Nook, my Macs (both of them), and my online BN library. My iPad when I get one. My phone if I ever decide to try and read on a 3" screen. Change one, change them all.
I'd also like to be able to automatically shelve books by author.
And then, going a step further, I'd love to see it automatically sort series of books. There are 20 books in John Sandford's Prey series, for example. It would be great if Nook and Nook Apps recognized them as a series and ordered them 1 through 20 instead of alphabetically - within a shelf. So they'd all be on the John Sandford shelf, in series order. That would also be a sales opportunity for BN - they could put an icon in there showing that you're missing a book in the series. I don't know that info is part of the meta data for a book, but it should be.
And finally, while we are syncing things, it would be great if the store knew which books you had already purchased, regardless of what device you were browsing from. When I got a new computer, the store had no idea what books I had already bought and downloaded. The info seems to be stored in a cookie instead of on the server.
I agree sorting by series should definitely be one of the next improvements to the shelves. Does anyone know when/if the next update will be? I'd love to be able to see/edit my shelves on my BN library too.