About the original question in post #1, I decided to pull the trigger and got the 16GB version of the Nook HD+.
At first, "adb devices" came empty. But after some hours fiddling with the settings and several reboots of my laptop, now the tablet is recognized and I'm able to sideload 3rd party apps using "adb install". Thus, I don't see a reason for rooting the tablet. At least not yet
.
Just for the record, maybe somebody is in the same situation, I followed the instructions found in
this page.