Fedup is a useful tool which updates Korora (and Fedora) systems to a new version. Chris did a good guide on the Korora Project site here. After trying it on a couple of systems I can add a couple of suggestions to improve your update experience. If you can add any others please do.
Non Standard Repos
If you use some non standard repos that don’t exist for the new version disable them before running Fedup. E.g. I was using the xfce 4.10 repo in 17 but as it 4.10 is standard in 18 it wasn’t needed. Leaving it enabled gave errors and slowed the update as fedup searched for it.
The Google repo is enabled by default in Korora and can be added to Fedora but for some unknown reason Fedup fails to update it correctly. If you have installed Chrome remove it before updating and reinstall it after. Your configuration & extensions etc. will still exist and Chrome will work correctly after re-installing.
Actually I also cleaned up my system first by removing some applications I had installed to try but don’t use now. This was a good time to remove them before they got updated.