One of the reasons mentioned that I like the Nooks is that they will dual boot first to the SD Card. This allows one to use third party ROMs to upgrade to full versions of Android.
You can download for Free a Jellybean image file, and create your own SD Card upgrade. So don't have to buy one from a service that is basically just downloading an open source Android ROM from one of the developers, and charging for it.
BTW, the stock B&N Nook HD+ runs Android 4.0 and allows one to install the Kindle app from Google Play. Not necessary to upgrade the ROM first to do so. Don't know if the Kindle allows installing the B&N Nook app at all?