Have you ever had to upgrade between major versions?

Been there, done that, gotta t-shirt and some bruises along the way

Linux Mint 17.3 Cinnamon to 18, using Clem’s tutorial.

Borked my Mint first time around. Had to reinstall.

2nd time got it right.

Put a fresh 18 on as a comparison, and went into Gparted and labelled the Clemmed one “Serena Clemmed” to distinguish between them.