Just did the update and now my Mac Pro 12 core won't boot. When I hold the Option key down there are two copies of my boot drive, but no recovery partition. When I did the update, it shut down as usual, but did not reboot - the fans came on and it just set there with the black screen. After 5 min or so I forced it off and tried to boot but nothing but the grey screen and no progress. I should have known better than to trust the auto updater - I usually use the Combo Updater for such things. Building a USB boot stick to see if I can salvage it.