Did the clean install dance over the weekend, knowing that I’d have a long weekend to get back up and running if things went pear-shaped.
Luckily they didn’t… kind-of. Had a few weird issues where High Sierra would copy the installer files to my newly-erased and formatted APFS internal drive, but upon rebooting would just load Recovery mode and not actually complete the install. Holding option at startup didn’t give me the option to start up from my internal drive, either — eventually fixed it by installing High Sierra to a spare external hard drive, then installing from that onto my internal SSD.
Coming from Yosemite, High Sierra doesn’t feel all that much different. Maybe slightly smoother, but honestly I’d be hard pressed to tell the difference.
Good job, Apple.
Brave. I guess if you back up with Time Capsule that’s OK, though.