no upgrade, really. I'm happy the way my system is running. Even when upgrading main apps (kde, gnome, gcc, etc...) doesn't give any trouble (hypotetically) why bothering in upgrade??, since usually the next release of the distros would include these new versions or even newer ones, and the distros releases are twice+ a year
I'm ok with upgrading minor apps like im's, p2p software and so on...