My booting experience
Just wanted to relate my experience attempting to boot from SD to flash CM 10.1 and get my Nook+ 32GB off the ground. Nothing really new to add except that I booted at least 30 to 40 times without any success, removing and reinserting my SD between each iteration. I FINALLY got it to boot into CWM and was halfway through my baseline nandroid backup of the stock ROM when, to my profound dismay, the device powered off without warning. After shedding a few tears, I began the process anew, and after ANOTHER 30 or 40 boot attempts, literally one or two trys away from giving up and shipping it back for a replacement, it finally booted again. I didn't bother redoing the backup and just forged ahead with the factory data wipe and installation of CM/gapp zips. After reboot, everything worked perfectly. This was three weeks ago, and I'm still going strong, installing ROM updates and enjoying my tablet, with no major issues.
Just thought I'd reassure anyone out there who is about to give up. I can't promise, of course, that you'll succeed, but I can state that you may fail dozens of times and then suddenly win big.
The only SD I used was a brand new Amazon Basics 32GB, which I wiped after copying nandroid to my Mac and have been using in my Nook ever since with no issues.
Patience, grasshoppers.