Hung Mavericks upgrade lost all users

Upgrading my Mini from 10.8.4 hung for about 6 hours with a nearly-full progress bar, so I tried to just quit and restart. That beachballed, so I finally did a force shutdown. When I restarted, I had to walk through the initial setup, creating a new user. I can now only log in as that user - while my other /Users folders are there, I do not see these users on the login screen.

Anything I should do before setting up a Genius appointment?