The Nook does indeed have the ability to create shelves like the Nook Color; it was part of their last software update. Sadly, afaik, you can't sort within the shelves, you just have to page through the collection until you find what you want, which can be daunting if you have a large collection.

I have a Nook and I do love it quite a lot, but it seems to me that B&N doesn't do a lot of marketing or successful marketing regarding the Nook. If you have a B&N membership card, it's not applicable toward ebooks at all. They generally have fewer free ebooks at any given time and they don't have the clout that Amazon does in dictating price, so their books are sometimes more expensive than the Kindle equivalent.

I don't know much about Sony readers, but there's really not that much functionality difference between the Nook and Kindle. I will say that B&N has, however, been very good about listening to what Nook users want, in terms of improved functionality (like the shelves) and have been consistent in offering software updates. I don't know if Kindle is the same, but I have liked how B&N seems devoted to improving the Nook you have, rather than forcing you to buy the next gen.