I upgraded from Fedora 25 to 26 alpha a few months ago and even then the process was smooth and the resulting system stable.
Haven't tried the KDE spin but I did try KDE neon briefly earlier this year. Quite slick but I quickly ran into broken package dependencies when trying to install some random stuff I needed (QGIS and sqlitebrowser IIRC); apparently it's been an open bug since September last year [0]. Didn't leave me with a good first impression but I'm rooting for the project - KDE is fantastic these days.
Haven't tried the KDE spin but I did try KDE neon briefly earlier this year. Quite slick but I quickly ran into broken package dependencies when trying to install some random stuff I needed (QGIS and sqlitebrowser IIRC); apparently it's been an open bug since September last year [0]. Didn't leave me with a good first impression but I'm rooting for the project - KDE is fantastic these days.
[0] https://bugs.kde.org/show_bug.cgi?id=368792