After making a clone (as Jon noted) & disconnecting all non-essential peripherals, I then ran the Combo updater.
As with other OS installs, a subsequent Repairing Permissions noted a great many repairs. Now it's back to normal.
I used TinkerTool System 4.11 to purge language support packages, of which there were many. Again, normal after any Apple install.
DiskWarrior 5.0 also found a few nits, but nothing major.
Other than cDock not yet working, easy-peasy.
