So, to let the cat out of the bag, getting a root console connection to the new Nook Glow Plus is quite easy.
There is a connector location, J4, which is quite clearly labelled with the pinout.
The output is 115200-8-N-1 on a 3.3V signal level.
TX refers to the output of the Nook, RX is the input, connect up ground, leave the V alone.
(Don't connect anything to this unless you understand the description above,
it's not anything related to a 9 pin RS-232 signal without a converter.
There are plenty of cheap USB-UART converters that run 3.3V that you can buy for $3.)
setprop persist.sys.usb.config mtp,adb
setprop sys.usb.config mtp,adb
Then you will have (unrooted) ADB over USB, which is still useful to load things.
Those who don't want to scuff up their new Nook would do better to wait a bit.