So far, there have been two real pain points: 1. Netplan is a mysterious friend who occasionally rearranges my furniture when I'm not looking. 2. Snap is a young kid who wants to make help me get groceries but borrow my car to drive to the store.
I'll leave netplan aside for a moment and focus on Snap.
I got 20.04 to fail badly under KVM using either the just released version or the nightly build because Snap fails. I can see exactly where it fails thanks to Python (cool). It's in an error handler for a UI view that's reading a property that doesn't exist and it hoses the install (ouch). It appears to be triggered because I was testing an odd network configuration.
Once something goes wrong, after that, every change just results in a one-line "apt-get fails" error message.
But consider the implications...
Canonical apparently doesn't have an automated testing system which checks how Snap behaves under failure conditions but they put it into the install process without protections around it. This feels pretty half baked....