I just ran the 13.1 upgrade for Slackware. For the most part it went well. One thing of note. Mysqld would not start.
The following error was in the log file:
100626 15:25:22 ERROR Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
100626 15:25:23 InnoDB: Started; log sequence number 0 1209759
100626 15:25:23 ERROR /usr/libexec/mysqld: unknown option '--skip-federated'
100626 15:25:23 ERROR Aborting
100626 15:25:23 InnoDB: Starting shutdown...
100626 15:25:28 InnoDB: Shutdown completed; log sequence number 0 1209759
100626 15:25:28 Note /usr/libexec/mysqld: Shutdown complete
I first focused on the errors regarding mysql-plugin, but after reading some forum posts,
I turned my attention to the 'unknown option 'skip federated'
I found the entry skip-federated in the /etc/my.cnf file and commented it out.
The server started just fine.
I then ran the 'mysql_upgrade to clean up the other error. Looks great now.