I'm curious about this too.
After today's longer drive, I'm still not experiencing any PB. SalisburySam has a Model 3, and I have a Model Y. I doubt that makes a difference, but my experience on AP is FAR from useless.
I tried it on Highway 401 (12-lane highway within Toronto) with lots of traffic, and it handled fine. Lots of cars cut in front of me, and it gracefully slowed down, and sped up. Even handled all "clover" shape exits. Tried lane changes, and I had zero concerns on how it handled each time. But one time, the speed sign went from 100km/h to 50km/h instantly, and it did precisely that. Tesla needs to handle this better.
Don Valley is a curly 6-way highway with some aggressive drivers. No problem there either.
Also tried on 4-lane (very tight and busy) roads, that was ok too.
In all cases, my left hand was gently holding the steering, the arm weight was just enough to not bring up any warning.
For the heck of it, once I turned it off, and I manually focused hard to stay in the middle of the lane. My wife told me the AP is better than me!
Overall, it is now much more relaxing to drive. Even my wife told me that. I have to drive this route weekly, and I'm looking forward in using AP from now on.