The decision to leave out profiles with a period was based on an internal (company) likelihood that a user may have already logged into the new domain and hence created a new profile which I didn't really want to touch. I would probably leave this check out for future migrations where we intend to run the profile migrator ahead of the user actually logging into the new domain.

SID History for us is brilliant. I haven't seen issues with many things, and it eases us from having to re-ACL entire directories when we migrate the users to the new domain.