The really awesome thing about Nook tablets is you can install a custom ROM onto a micro SD card, boot off that, and leave the stock image on the internal storage untouched, basically allowing you to dual boot between stock Nook and the a custom ROM.
You will need a good micro SD card with fast 4K read/write performance to not slow down the custom ROM on the SD card too much. Most Sandisk microSD cards would be a good choice for this.
One good benefit of using a custom ROM on the Nook HD+ is being able to pair a bluetooth keyboard. Nook's stock UI has a bug that doesn't allow you to to pair BT keyboards or any device that requires a pair code.
Nooks stock UI isn't all that good in my opinion, you can add a third party launcher on stock Nook, like Nova and it helps. But it still doesn't fully resolve the stock UI weirdness. So putting a custom ROM on the Nook HD+ really helps it feel like a familiar Android device.
Standby battery life has improved with CM11. But I don't think it's still as good as Stock Nook. So that'll be a sacrifice.