Originally posted by timw4mail A bit of an exaggeration. Non-flash drives aren't automatically converted to the new file system, but they can be converted. Fusion drives are not supported yet, but I suspect that is due to a late-running bug, judging by the back off from the pre-release versions.
I just based this on an article in Ars Technica which stated the new file system only supported systems with all flash storage at this time. They most likely will fix this. While all flash is becoming common in computers these days, a lot of people are still using hard drives for external storage, backups, etc and I can't imagine Apple not addressing this.
For me, I'm never in a rush to update. I always wait a couple of weeks because there are always issues that pop up.