My Razr M (98.18.94.XT907 has never been rooted. When the OTA upgrade to Kitkat was pushed I began receiving it and trying to install, but it failed numerous times. I finally reset the phone to factory and wiped all data and did the minimum setup (no accounts).
The OTA upgrade still downloads successfully but gets only about 40 percent through the install and fails.
I'm timid about rooting but am willing to try just about anything at this point. The constant upgrade reminders (and the periodic downloads) are beginning to drive me nuts.