I just moved everything important to another hard drive (including copies of My Documents and all the other Windows system folders where games like to squirrel saves away... basically I copied almost my entire 500gb boot drive to my 1tb backup drive), took screenshots of my start menu and desktop (so I wouldn't forget to redownload all the little helper apps you accumulate over the years), and then let the 8.1 installer format my boot drive. But my 7 installation was old and bloated and had been getting a bit weird so I welcomed the opportunity to start fresh.
I found getting everything back where it should be was pretty painless? It helps that with Steam and Origin etc. most games don't care if you move them around or change the OS, as long as you make sure you have copies of their saves; back in the days of XP it was a nightmare reinstalling every bloody game from DVD because they liked to shit random crap all over your HD and registry. Once I've gone long enough I can be sure all my game saves and documents and such are back in their rightful places I'll delete the backups and get some hard drive space back.
Ninite helps a lot. The PC Gaming Wiki might help you find save files you can't track down. And the first thing I did when presented with my shiny new 8.1 desktop was install Classic Shell.
Sounds alot better than before. I guess i've just got old memories of moving from XP to Vista to 7.