This morning the pinwheeling has stopped. Apparently although the system was operational the HFS+ âž APFS conversion was still going on in background. I am a much happier camper!
Because of my own curiosity and because of the interest indicated here, my initial explorations are going to be centered around APFS. At this point the only difference I have noted (other than several hours of pinwheeling) is Disk Utility says the boot drive is formatted APFS. At the moment I am looking for a way to non-destructively convert my other drives. So far I am having no luck. Disk Utility will happily format a drive APFS, APFS (Encrypted), APFS (Case sensitive), or APFS (Case Sensitive, Encrypted) — but unlike High Sierra's installer, all are destructive.
CAUTION I just opened Photos and the first thing it did is update the Photos Library. This does not bode well for any of you who might want to run Sierra (or earlier) and High Sierra. You are going to have backward compatibility issues.
