So I'm sure some adaptive cruise controls are better than others but coming from a BMW X5, the range of the sensors would result in situations where traffic would speed up, a car in front of me would change lanes, adaptive cruise is set to 65 mph (because we're on the highway, even if we're crawling along) so it speeds up because it thinks it's now "open road" but the cars in front of me are already slowing down because of another bottleneck ahead so it has to slow down quickly once it detects them.