[appending to Todd's list of 07:27]
9. In my experience, migrating a root partition from Mandriva to Ubuntu, leaves the user account(s) with the wrong owner (!) due to different default UID range. I did chown -R and moved on, but such a snag would likely be unsolvable for someone without command-line experience. Newer versions of Ubuntu installer may have resolved that, i'm not sure.
