Right before Apple releases a new macOS they release the GM (Golden Master) Candidate. That is the final version of the OS that to be released to the public. As an Apple Developer I was able to update to the GM candidate of High Sierra in my Beta install. I have it installed as an APFS volume. Nothing startling to report, it seems to work fine. It is definitely fast, but we will see when it gets installed with my myriad of applications on my main drive.