I like the Ford approach of focusing on augmenting and making life easier for drivers, but not pretending that we are at the full self driving stage yet. Keep driver engaged at all times but have him do as little work as possible.
I used adaptive cruise control on 2,000 mile trip this summer and really only had issues with long steep curves or wherever things were extremely windy.. it needs be intelligent enough to know that some areas you should reduce speed and others, like where flat and straight should increase. I found myself constantly adjusting the set speed. But, once set, it worked perfectly.