Upgrade from Ubuntu 12.10 to 13.04 smooth as X-Lax
The upgrade was "smooth as X-Lax" (an over-the-counter brand of laxative).
1) Shutdown Linode
2) Duplicate file image in case of problems
3) Start Linode
4) Login using LISH in case of disconnect
5) As root, run the command do-release-upgrade.
6) It asked if I wanted GRUB installed, I said NO.
Apache did not start after the first reboot
All is well according to my tests.