Now that Mojave is about to be released I have been thinking it may be safe to upgrade from Sierra to High Sierra on my Retina 5k, 27-inch iMac (late 2015 design, purchased 04/17). I have avoided it because of the problem with APFS not working with fusion drives.
I saw reports that APFS will work with fusion in Mojave but does anyone know what the status is for iMacs with a fusion drive upgraded to High Sierra? I assume (hope) the update will be smart enough not to trash my drive and leave the file system as is.
I’m personally skipping High Sierra and going straight to Mojave on my late 2014 retina 27" iMac. Nothing really to be gained with High Sierra, IMHO, since the big deal with that release wis APFS. Sadly, with either upgrade I’ll have to retire a bunch of programs that work on Sierra.
The only thing I saw in the “what’s new” documentation that I cared about was the claimed increase in security. That and perhaps a lighter footprint for the OS itself making it slightly faster.
As for Mojave, I never even consider installing any new OS untill it has been out for a considerable time and had several bug fix updates.