After several road trips with autopilot, I've noticed that it is very good and very stupid.
Phantom braking is a constant source of irritation. We want products to fail safely, but an uncomfortable ride makes things unsafe. Too many incidents of boy cried wolf desensitizes people to alerts and warnings.
Auto pilot was clearly designed for controlled access highways. Even then it makes questionable decisions. There are times the car wants to change lanes with absolutely no traffic or navigation. The car will pass slow moving vehicles but then never return to the right lane. However, when I was in the HOV lane I had to cancel the change lane every 30 seconds. It even tried forcing me to change lanes through double white lines.
When working as intended auto pilot reduces driving fatigue. Theoretically it should consistently drive in a safe manner and not make human mistakes causing an accident. In practice you still need to be alert and observant ready to take over at a moment's notice.