I performed upgrade to 12.10 from 12.04 using update-manager. Unfortunately, there was some error, because when I came back from the coffee, the screen was black.
I opened a terminal (Ctrl+Alt+T) and killall dpkg, which seemed to be waiting for user input for configuration file update (xdg package , if I remember well).
After that, I did a do-release-upgrade, which seemed to work well, because I ended on a graphic session after reboot.
The problem is that some 12.10 features are missing, as Online Accounts and Dash new online results. This made me suspicious of missing packages or something like that.
Please take a look at upgrade logs and my new dpkg --get-selections output: https://gist.github.com/3919006
dpkg --reconfigure -a didn't solved the problem nor apt-get -f install showed any problem.
do-release-upgrade say my system need no news packages (even if I change /etc/lsb-release to 12.04)
If someone give me a dpkg --get-selections of a vanilla 12.10 installation, may be I can force system reconfiguration.