Nah old fashioned root method is safer and guaranteed to work... i wouldn't try that way. An old man in ancient times (1990's) once said "That which is on youtube is not always true" and it remains true to this day
Search google or xda forums, they are specifically for the atrix. I unlocked and rooted my atrix by sbf flashing into a controlled softbrick, entering fastboot to unlock and then reboot. Ding fries are done! Make sure you read the instructions all the way through before attempting any install.