My InstallationMedia is 9.10. I had one troublesome update where it only partially completed but it was happy to complete it after a reboot (11.10). Other than that, I believe I have only had one thing function other than as I would like. In the upgrade to 12.04, it hit a point where something I had changed in /etc (turning off AppArmor for Evince, so that I could use a custom hyperlink protocol, which made it easier to work with Lilypond) caused it to stop, awaiting a decision from me on what to do with it. As a result, I got up in the morning and lo: it was only a third of the way through. Not what I had intended.