I know this is probably obvious to you, but having your HOME directory on a
separate partition is really really helpful. The OS installers will leave it
alone if you switch from Ubuntu to Trisquel and vise versa and since Trisquel
is based off of Ubuntu, there shouldn't be too much of an issue with
settings. For example, if you used Firefox on Ubuntu and use Trisquel's
Abrowser, your settings will be the same due to Abrowser being based off of
Firefox.
Since I do development, I have files in my own HOME directory and a
public_html folder for nginx to use on the HOME partition. Since some .conf
files are referenced in /etc/nginx, I simply moved those to a /conf/ folder
in public_html and created symbolic links in /etc/nginx to them.
Other non-Debian based distros like Fedora/CentOS, SuSE, and Slackware can
use the separate HOME partition, but I haven't really used them and not sure
if the settings stored there can be easily referenced with Trisquel.
I know this may or may not be important, but if you are switching from
Ubuntu, isn't it best to have the versions sync up to avoid issues with the
settings? I ask because I assume moving from Ubuntu 11.10 to Trisquel 5.5
would be ok since they share the same codebase, but moving from Ubuntu 12.04
to 5.5 would maybe create issues.
Its too bad there are no Trisquel 6.0 ISOs if he is moving from Ubuntu 12.04
to ease the transition.