I came for the filesystem bugs, I stayed for the absurd root exploit, but its the little crashes, rendering glitches, and feeling of general instability that made me fall in love with High Sierra...
Unfortunately, it seems Apple has forced us to choose between Meltdown mitigation and a somewhat working OS. The recent Sierra security updates didn’t include the Meltdown patch.
My educated guess, based on 14-years working for MIT’s IT department: the fixes for Sierra and El Capitan broke something important, so they got pulled.
My MacMini6,2 (2012 Server) has two SSDs RAIDed together. High Sierra beta worked fine and upgraded fine to golden master and subsequent. When I decided to reinstall my OS from scratch and reload from backups I discovered to my horror that mine was not a supported configuration and there was no way in hell I would be getting back to where I started from. This happened on the 20th November. I finally managed to boot my system again on the 20th December. After failing to re-enable RAID I broke my system into individual root and /User partitions on separate drives (or tried to) and discovered that APFS (Encrypted) and /etc/fstab don’t get along. I re-defined my home folder to be on the second drive but cannot log in until I’ve logged into a utility account and mounted the encrypted partition separately. Currently permissions are so fucked up I can’t even stream music from iTunes. On Monday I’m gonna nuke it again and try another route from scratch.
Throughout this Apple Support has been anything but (aborting when for some reason my Mini’s S/N failed to match their records for Server machines, and thus bailing on me on the premise that I shouldn’t have RAID anyway so basically screw me.)
I've felt for a long time that Apple have lost interest in their end-user computers. MacOS Server has long seemed like 'if you REALLY want it, here, have fun'. But the tools tended to work. SoftRAID somehow works fine on Windows, why not on Mac.
Can't imagine how much pain you've been through with this. Got enough backups to revert back to Sierra?
Maybe not on 1 billion devices, but ZFS was running on mission-critical Sun/Oracle hardware with expensive support contracts for many years. ZFS is currently probably the most reliable modern filesystem.
Still, rolling out APFS on such a large number of iDevices/Macs is a very impressive feat (although APFS is, of course, a simpler filesystem). The problems are with many of the 'edge cases' (RAID, etc.). This is not really surprising, btrfs has been in development since 2007 and still has problems with more complex setups.