Exactly the same experiences here. My MSI-laptop (with NVIDIA on board) needed a fresh install to Mageia 6, because re-partitioning was needed in my case.
The older desktop-machine went smoothly through the upgrade-procedure from Mageia 5.
My brothers' laptop i upgraded remotely through a SSL-connection, and also that was no issue.
Now i have Cauldron in VirtualBox, besides openSUSE-Leap and openSUSE-Tumbleed VM's. All of them up-to-date.
Though, it must be said, i had to reinstall Cauldron one more time, after one update-session went miserably wrong when systemd-update hanged and frooze the virtual machine. After reboot i was left with only a grub-prompt.
I also fiddled around with the other desktop-environments, and must say, was pleasantly surprised by XFCE, very neat.