Hi Colleen,
Thanks a lot for such an awesome explanation for the technical upgrade.
I have another question related to the Security Upgrade.
My customer had a list of roles which are known as emergency roles and they suggested to replace the new open authorizations as * and for other roles, they suggested to deactivate the new open authorizations. But due to some miscommunication, I had started fixing the roles in vice-versa way. Although not all roles are fixed but 135 are already fixed in this manner.. 
Please suggest whether the original state of the roles can be reverted back in this case.
What I have learnt from this blog is that we cannot revert back the changes we have done. But I want to know that if I download the roles from the Production(Non-upgraded) system to the DEV box and re-run step 2C, whether the original state can be acheived for the roles I have already modified.
This a very urgent issue. Quick responses will be greatly appreciated.
Thanks in advance,
Vandana