People,
I just updated from F20 x86_64 to F21 via fedup and although it took a while - it was completely painless!
The only thing that was odd was when downloading RPMs (console) parts of one line would be duplicated over the whole screen and then letters would start disappearing (an odd screensaver thing?) - I don't know what that was about but it was just a display thing and pushing SHIFT caused a sensible output again.
The only package issue was some dependency problem with pdftk but I will worry about that later.
Thanks again people!
Regards,
Phil.