Can't upgrade from 10.11 to 10.12 via software update as as soon as it tries to boot from Sierra it causes a kernel panic. Luckily I had a time machine backup and reverted back to 10.11. Machine was fine again. Did a clean install of Sierra and that worked fine, but when I attempted to install files and Apps from time machine backup, Sierra caused a Kernel Panic again. Guess it does not like one of my Apps. Deleted all of the Apps that load into the System Preferences pane, but it looks like it is not one of them, as tried again to update and same kernel panic error. May wait until .1 release comes to see if that solves the problem. Somewhat frustrating.