In High Sierra they painlessly replaced the filesystem.
No, they did not. They still cannot upgrade any Mac mini server running RAID 1. They sold that configuration and crippled there software to put in the new file system. That is only painless for flash drive owners.
So what pain did it cause you? Your computer is running the new OS, and they’re doing a staged rollout which seems to have caused no problems – that sounds exactly as described.
My computer is not running the new OS since it cannot be upgraded currently. We are upgrading every other Mac (originally for fear of not having the latest security), but cannot do upgrades on a configuration sold by Apple. Their filesystem transition which was accompanied by a down grade of Disk Utility is not painless.
No, they did not. They still cannot upgrade any Mac mini server running RAID 1. They sold that configuration and crippled there software to put in the new file system. That is only painless for flash drive owners.