Servers booted into 13.04 fine the first time after the upgrade, although I still saw the MOTD notice "New release '13.04' available.\nRun 'do-release-upgrade' to upgrade to it." after booting into 13.04
So I refreshed apt (update / dist-upgrade... 0 changes) and rebooted again...
This time, rather than completing the reboot...:
still pingable, but sshd dead... frustrating for dedicated servers* Asking all remaining processes to terminate...
* Killing all remaining processes... [fail]
* Will now switch to single-user mode
Give root password for maintenance
(or type Control-D to continue):