I have Adaptive Cruise Control (ACC) on two of my vehicles. My Subaru ACC works great in most situations. It's very sensitive and it's saved me more than few times when the sun was setting behind me lighting up everyone's tail lights making it hard to see who was actually braking. The worse cars to follow are the old junkers with the dim tail and brake lights. When the sun is shining on those heaps, you can barely tell if the driver hits his brakes.
The only downside to the Subaru ACC is if you're going at say 70 mph and then traffic slows down to 45. It'll properly slow down to 45. But then say traffic speeds back up but then suddenly slows down again. If the car is still accelerating to get back up to the preset speed of 70, and traffic slows down massively again, the ACC waits too long IMO to hit the brakes. This results in late emergency braking unnecessarily which of course sends my pulse through the roof.
It's also not infallible in heavy stop and go traffic when people cut in front of you suddenly. The ACC won't activate fast enough to avoid a collision. Well it might, but I've always chickened out and hit the brakes myself before I got too close to the other car.
So basically you have to learn the proclivities of your car's system. No system is perfect and you are the driver so you must be aware at all times.
That said, the system is generally wonderful, especially in stop and go traffic.
The reason I got the Ford Superduty truck was because it has the ACC that can be used when I have a trailer hooked up. It also has the blind spot indicators that can be used for a trailer up to 33 ft. My trailer will be 34 ft, but with the overlap since it's a fifth wheel, I should be able to use the blind spot monitor. Not that I'll need it with the rear observation and lane change camera, and those giant mirrors on the truck.
