Doing a sanity check.. is anyone else getting kernel panics on beta 9? I'm running it on a 2014 27" 5K iMac and the machine locks up a few minutes after login or restarts on its own.
What's your Console say prior to "BOOT" messages, around the time of the kernel panics? What do the kernel panic screens look like? Have you checked there are no bad daemons or Launch Agents executing on login (EtreCheck is extremely helpful here)?