I bought the Nook the week they came out, after researching the hardware available at the time, and after seeing the screen at the store. It had, at the time, a really nice screen, and I still like the screen. However, I didn't realize that only the B&N app store was going to be available. As someone said, above, the B&N app store is a ghost town... though I must admit they do have, literally, hundreds of apps. The browser interface, to be charitable, sucks. The book app periodically freezes necessitating a hard reboot. It did not come with a calculator! To be fair, the book app IS fast, and pleasurable to read with. I've heard that you can copy and paste from some of the apps, but, none of the apps I have have copy and paste.
I wanted a tablet so that I could retire both my Sony eReader and my iPod Touch, having just one device that would fit my back pocket. The Nook sucked so much that I was not able to retire my iPod... When the Nexus 7 was announced I was a little more careful in evaluating it. With it having Android 4, and access to a large app store, I was satisfied that I'd found the replacement for the Nook. I pre-ordered it, and have been happily Nexusing since. It doesn't have quite a 'retina' display, but, very dense, and quite pleasing to use. I was able to get all the essential apps that tied me to my iPod. I bought the 16GB version, and was not irked by the lack of addon memory.
Postscript: However, it got run over last week by a car and the screen protector failed to protect it... And I discovered that all the data that I had on the device was now locked inside a brick. NEXT device I get will either have addon memory for all user data, or some kind of cloud sync for ALL user data.