Today I decided to try a remote upgrade (Ubuntu 8.04 > 10.04) on this server.
Following the official instructions, the process when very smooth:
https://help.ubuntu.com/community/LucidUpgrades
This saved me a trip to the data center!  8)

If you are planning doing this, make sure you either know the changes you made to config files or make copies
of them before starting so you can install any new versions of packages.  The ones I had to modify are:
Dovecot
Apache
Logrotate
Proftpd
PHP