Ubuntu 14.04 LTS
Well, that was fun.  The upgrade crashed halfway through.  I rebooted in recovery mode, finished the upgrade using the dpkg repair option, and then restarted a few times and found that it still wasn't working.  Looked like a video problem, so I checked /etc/X11 and found the xorg.conf files had been backed up and not replaced.  A comment in the last one inspired me to run nvidia-xconfig and it worked fine.  Pretty typical when you use Nvidia drivers, and still a lot less painful than upgrading Windows XP to 7.