Doing the upgrade
At first, since the installed version was a LTS one, I had to enable notification for any new versions in the “software sources” configuration.
after some more confirms the long download started
the upgrade proceeded smoothly until I got an error message about some missing files. It seems that the Italian server I was downloading from was incomplete (at the moment I was upgrading). After playing a little with the software sources configuration I managed to find a complete server. The upgrade restarted (downloading only the missing files) and eventually completed.
After rebooting I gave quickly verified that Unity was running fine (I don't use it but my wife does), then got into my usual Gnome-Shell environment. I was a little surprised to see my desktop environment stripped of all extensions I had accurately chosen in the previous installation. It happens that older extensions lost their compatibility with the Gnome-Shell version (3.6.1) that comes along with Ubuntu 12.10. Fortunately most of the extensions I was using have already been upgraded by their authors so a quick tout in the gnome extensions page was all I deeded to restore most of my desktop.
This Ubuntu upgrade concluded in e relatively smooth way, without big problems. My Veriton S661 runs as better than before: the upgrade seems to have solved some minor glitches the previous release had in handling the video card. On the other side I hope not having to look for an upgraded release of my Gnome shell extensions at every major upgrade of the desktop environment. Extensions are an important part of the Gnome shell, they are the reason I use Gnome 3 even I don't like the “mainstream” way its interface works.