The 'upgrade to next version of ubuntu' has gotten pretty good these days.

The only thing I would make sure to do is to have a separate home partition / volume so if you had to blow the underlying OS away after a botched upgrade, it's easily doable.

For the life of me I don't understand why having a separate area for your personal files isn't the default on every OS. Just pick a reasonable size for the OS part (20-30G?) and give the rest to /home