I find the adaptive cruise control on our Skoda really good. I use it loads on dual carriageways and motorways, also for average speed camera areas and extended 30 zones (not london).
I find it is a safer driver than I am on dual carriageways / motorways as it doesn't tailgate (not that I generally do but sometimes frustration takes over when approaching someone bimbling along at 60 in the outside lane). It is also better at judging how hard the car in front is braking, or what the approaching speed differential is.
OTOH my father's Subaru has that lane departure thing and it's just a bloody nuisance on A roads. Can't find a way to turn it off, either.
I fully expect autonomous vehicles to be safer than human driven ones.