I have an MBP TB and I was away on vacation, I kept my mac plugged in to allow it to install the PB update. When I got home today it said something about a file being missing or corrupt and to restart. Restarting the mac showed the same message. I went into recovery to reinstall MacOS and my drive was missing. I formatted the drive and started the install and midway through it displayed a circle with a line through it. I reformated again and the install went through. Just thought this was interesting as I have never experienced anything like this with a mac. Also, I realize it's beta software and I'm not complaining.
TLDR Back up your stuff.
TLDR Back up your stuff.