Sorry for the late answer, but "yes" would be it :)
There's a link on the user info page (the one that let's you "become" a user, etc) that lets you make a user a site wide admin.
If you haven't guessed already, I wrote an upgrade script that changes references to the old security_context_root to the new one.
And code that referenced "0" rather than the symbolic security_context_root was ... broken and should be fixed regardless.
