I use Autopilot every day. I think it's amazing and borderline life-changing if you are like me and dread the monotony of a daily commute. I don't think most people realize just how mentally fatiguing the act of driving (constantly making all sorts of micro adjustments) is until they use Autopilot for a while and see the difference for themselves. I certainly didn't. I can now drive for many hours and feel just as alert as when I first got into the car. I was never able to do that before Autopilot.
Yes, you still need to pay attention. It is hard for me to believe that any Autopilot user doesn't know this because you learn it by experience almost immediately. People text and drive all the time in manual cars, but for some reason when they do it in a Tesla, we declare that Autopilot lulled them into it.
While I agree that you need to be ready to grab the wheel or hit the brake on short notice, I disagree about what that means. There is a big difference between having to be ready to do those things and actually having to do them every few seconds. This difference wasn't intuitive to me, but in practice I've found it to be extremely mentally liberating and true beyond question.
I've also found that Autopilot makes it easier to take in all of your surroundings and drive defensively against things you otherwise wouldn't see. One thing that has struck me, as I now see more drivers than just the one in front of me, is how many people are distracted while driving. If I glance continually at an arbitrary driver on my way to work, there is a greater likelihood than not that within 10 seconds they'll look at a phone. That is terrifying to me, but it is also good information to have as I drive -- I am now able to drive defensively against drivers around me, not just the one in front of me.
I've also found I'm more able to think or listen to music or podcasts than I was before Autopilot. I could never get much out of technical audiobooks, for instance, while driving manually. But Autopilot has changed that. I hesitate to say this because I worry that I will give the impression that I am focusing less on the road, but I don't think that's what's happening. My mental abilities feel much higher when I am not constantly turning a wheel or adjusting a pedal. I'm listening to music, podcasts, or audiobooks either way -- I just get a lot more out of them with Autopilot. I think it goes back to the lack of mental fatigue.
Whatever you make of my experience, I urge you to try it on a long drive if you ever get an opportunity. I have put over 60k miles on Autopilot, I have taken over on demand hundreds if not thousands of times, and I've never had a close call that was Autopilot's fault.