Not about G80, but rather about the G90 long term test experience by Autoweek magazine (March 12, 2018). Overall they said the G90 was as close to perfect as a luxury car has been in a while. Not a performance car, but a luxury sedan. Very reliable, comfortable, easy to operate electronics, etc. More user friendly than the German luxury cars, especially electronics and ride settings.
Concluded by saying M-B and Audi probably don't have anything to worry about - yet, but Acura, Infiniti and Cadillac should.
Only drawback is lack of badge prestige.
G90 sold 4,400 in 2017 which is a small number, but that was pulled out of the other lux brands during a dramatic downturn in the sedan market. Spotty advertising and a lackluster marketing campaign contributed to poor sales. Could probably add in the dealership situation (or lack thereof). For me, it is a one hour drive each way and after three years, no concierge service.
Regardless, it is an extraordinary car and at a lower price than the competition. Hopefully it will improve sales. More importantly, hopefully this G90 progress will transfer to the G80.
Motor Trend recently had a super favorable review of the G90. It bested BMW 7 and Lincoln Continental and will later be tested against the M-B 'S" Class.