In traffic is where traffic aware cruise control is most useful. A lot of people I knew who bought Tesla's in the bay area specifically bought it so their commutes would be less stressful with the bumper to bumper traffic. I drove 3000+ miles across the country last year with > 90% of it on AP and I was way less tired with AP on vs off and it allowed me to just stay focused on the road and look out for any issues.
One thing worth noting about Subaru's approach to this that is specifically relevant to bumper-to-bumper traffic, is that it will stop by itself, but it won't start moving by itself - the driver needs to tap the accelerator for that. It will warn you when the car in front starts moving, though.
Yes. I was (explicitly) talking about traditional "dumb" cruise control. I haven't used adaptive cruise control but I agree it sounds more useful than traditional cruise control once you get above minimal traffic.
