I updated today. Except for very slow download speeds (undoubtedly due to Apple's servers being overextended), all went well. Probably, downloads will speed up considerably in a day or so.
Overly cautious perhaps, but I first disconnected all peripherals, ran DiskWarrior, restarted In SafeBoot, and from there, ran the Combo updater. Total elapsed time: 35 minutes.
FWIW, I had a "Cocktail" artifact in System Preferences/Notifications that I could not delete. OS 10.11.6 resolved that issue.
AFAIK, no problems.
Harv 27" i7 iMac (10.13.6), iPhone Xs Max (12.1)
Those who can make you believe absurdities can make you commit atrocities. ~Voltaire