I upgraded to 13.04 no issues. A couple of the other user accounts had passwords that worked in the previous version, but weren't meeting the minimum password requirements in this version. I didn't want to change the password, till they logged in at least once so that the home directory synced.
I tried the
sudo passwd <username> command. The password took, and I am able to login to one of the terminal screens. But if I login to the GUI, I get kicked out immediately (with these accounts).