I just did the migration successfully today after no d-u since 25 Nov . As the kdenext repo is now empty, the instructions regarding saving the package list and replacing with sid packages no longer work.
All I did was remove kdenext from sources and run update then dist-upgrade. I neglected to purge qml-module-org-kde-activities before starting but managed to force it (can't remember if aptitude or apt-get -f install or both). Plain sailing from there.
I don't have kde-full or kde-standard installed but seems ok so far.
903 upgraded, 34 newly installed, 13 to remove and 0 not upgraded
digikam and okular were both able to be installed by aptitude afterwards, forcing "downgrades" to the sid packages and dependencies.
There are 77 packages listed as "No available version in archive", I'll sort through them later.
Ultimately I'm amazed it went so smoothly. Time will tell if there are hidden issues but looks fine so far.