Peach “Fuzz” FaeStatus Report:
Well, just finished upgrading my four machines from LMDE 6 - 7.
I give the process a 5 out of 10
None of the four could run mintupdate successfully. Each one barfed for different reasons. None of the failures killed the machine.
A wipe & scratch install worked fine (although not flawlessly) in each case. (I have good backup strategies quite independent of Timeshift and its ilk, although I do that too).
In short, no worse than an APPL or DOZE update.