After an unfortunately failed experiment at releasing the Droid root exploit after raising money to buy himself a Droid 4 and $300 to charity, the creator of the exploit, Dan Rosenberg has released his root which works on 2.3.6 entitled "Motofail"
You can download it from the link above and it should be able to root 6.12.173 on Droid RAZR directly without having to OTA rootkeeper 748 and upgrade.
Enjoy~~
And please consider donating to his fund which is still at the link. It all goes to the Red Cross now.