[Samba] Best strategy to move/upgrade Samba 3 PDC to new Samba 4 server

[MI]

>> And of course, the important related question: Keep it an NT4 domain, or
>> upgrade to AD?

> Reading this list and the wiki and looking at the seemingly endless number
> of options for smb.conf makes the upgrade to AD seem pretty intimidating,
> and like you, I don't see any real benefit for our organization. One
> concern though, is that future Windows workstations will pretty much expect
> to be part of AD domains, so problems will begin to appear on NT domains.
> Already I see hints of issues with Windows 10, but I don't have any
> experience with that yet.

I am really tempted to just setup my new server as a BDC, and then promote it to PDC 
and remove the old server. But the scarcity and old age of documentation about this 
worries me.

And I do need to support Windows 10 for a few new Surface Pro 3 machines.

It would be nice if someone who has already done this would tell us how it went.