Ok don't know how much traffic this forum gets but figured I would throw this info out there incase anyone gets stuck in a boot loop after OTA.
Having rooted my Ultra I let the OTA come thru and hit install before I realized that I forgot to unroot and got stuck in the loop, after several articles, downloads, hair removing frustration, none of the files posted online for the Ultra worked for either house of moto program or RSD.
So I finally decided to try the obake_maxx_xml file located here Droid-Developers SBF
and followed instructions located here http://www.andromods.com/unroot-locking/unbrick-droid-ultra-back-xt1080-stock-factory-firmware-rsd-lite.html
to open the zip, find the xml file, open it in notepad and remove the line with "getvar" and save it. Neither of the other two files worked for me.
Fired up RSD pointed it to the folder where the obake_maxx file is and plugged my phone in to usb.
Just incase anyone forgot like I did, you need to get into settings of your phone while it's looping and make sure usb debug is OFF.
After you do that you need to shut the phone off during it's loop and before it turns itself off so the phone doesn't turn back on.
Now with it turned off press and hold the power and volume down buttons for 3 seconds and release both, that should put you into fastboot mode.
RSD screen should now show fastboot in the phone section, now just click start and sit back, when it's done the phone will shut off and RSD will state to manually turn phone on. At that point your done and now your looking at the setup screen you first saw when you got the phone.
Just to put minds to rest I am including two screen shots of my phone info so you can see that it does NOT think it's a maxx, I believe that part is burned into rom.
These pics are after the OTA because that maxx xml file is apparently the original software the phone ships with.
Once the phone started downloading all the saved apps and contacts etc from google backup I noticed I was getting an OTA and let it run.
Life is good.