I gave the adaptive cc a try last week on a moderate to lightly populated freeway. It actually worked very well. I do find the "bumper guard" effect of the lane centering a tad irritating, and as others have mentioned I feel about 6-10 inches too far in the right of my lane (I imagine Toyota was biasing against head on collisions at the expense of crowding drivers to your right...but now that I think about it, is the software the same or reversed in Japan since they drive on the left?).
That being said, it did serve to keep me more alert than a full self-driving car would and was still less effort. I was particularly impressed by the responsiveness and display graphics when someone cut in front of me (I'm currently trying the "two panels" of distance in the system and it feels about right); the system responded as quickly as I would have from the time the car started cutting into my lane. I think that's the one thing these systems haven't achieved yet; I've got 40 years of driving experience and can usually "feel" when someone is about to make a shift / move. The software can't do that yet so I feel the response is "delayed" but it was actually more than sufficient.
I also used the TJA function and found it works as advertised, even in the 20-25 mph zone where the braking required was more significant. I was hovering over the brake pedal the whole time, so it was actually more stressful than just driving, but I wanted to know the system limits. I think TJA is a great capability in literal slow speed stop and go such as an urban traffic jam or when there's been a pile up ahead of you on the freeway.