It would be my bias as well, you would want to keep your account under your own lock and key and not Microsoft's as that would mean giving away far too much control from a security perspective.
Luckily, the change is only a few steps away, hiding in Control Panel, User Accounts, change account type and select Local Account.
I would suggest, based on the above that users do that before doing the upgrade. All it takes is a logoff and a logon before applying the upgrade. For those insisting on handing over control to Microsoft for reasons I would not know, they can do so after the upgrade is done.