What to save in addition to /home when upgrading?

[zacktu]

When giving advice about upgrading, everyone says to save (or not reformat) /home. Using the contents of my old /home partition should tell the updater that I have installed programs that are not part the the initial installation so that those programs will be reinstalled. The advice seems to stop there.

It seems to me that some other files are essential. Several other files I'm going to save are /etc/hosts, /etc/samba, and/etc/fstab (at least for reference if not copying). What other files should be saved in preparation for an upgrade?

[Pasdar]

I didn't save anything, and I left everything in my home folder too. After upgrade everything worked and what I had changed was still changed, and things I had put on it were there too.

[logos34]

maybe /usr/local and /opt (if anything's there)