The NSRT worked perfectly for me. Just needed to reinstall Update 1. Finally have Cyan, took long enough!
I ended up using NSRT to reflash my ATT 920 to Cyan 8.1. After backing up my stuff, it was a one step process. There wasn't anything in 8.1 Update 1 DP for me to miss anyway. My phone is a bit more stable after flashing.
Did you just use the built in backup, or did you separately backup photos, videos to your PC? Also, did you lose any settings, app settings, start screen or anything at all? I'm tempted to go ahead and use the NSRT; I'm assuming it will clear out my 5GB of Other and hopefully make my aging 920 snappier.