What are some challenges you typically face when making system or software upgrades? (QuickBooks or otherwise)

For me personally, it's forgetting to make backups of my work before I make an upgrade or update.

I've learned the hard way many times (guess I am a bit slow). I am now very OCD about backing up files to a secondary hard drive on my computer as well as a removable hard drive I keep in a safe (yup, I do).

This way, I always know my restore point.