I strongly recommend that you try upgrading with 'fedup' next time around. It's far-and-away better than our historical upgrade processes and works in-place. I've personally gone from F17->F18->F19 using it with no ill effects.
I had a lot of problems with fedup from 17 to 18. They were fixable after you figured out the issues, but, it caused problems on two systems anyway. Apart from that, the update problem has been pretty tame. Things have been sufficiently stable that I no longer update with a full new install in its own partition while retaining the original so that I can backtrack. I probably should, but I don't.