FWIW, I just upgraded from beta 5 to beta 7, and my MacBook Pro 9,1 (2.7 i7, 16GB, 512GB Apple SSD) went through about four reboots in the processes. One was clearly an EFI or SMC update (I would like to know what that was for) then after about three more reboots, it allowed me to log in. The App Store had message in the notification center letting me know that "Some updates could not be installed automatically. I went to the App Store and was greeted with the attached message. I selected "Install" and it restarted again (perhaps twice, I can't recall) and came back up and all seems fine, and no additional updates are available. The disk is using an APFS filesystem.