I am very comfortable with it. But that being said, I am a tech enthusiast and use it responsibly - I understand its limitations and functions fully and as a result know when and when not to use it. I never take my eyes off the road while it's engaged and I don't use it in high risk areas (like construction areas).
I have already put 700 miles on my LR AWD Model 3 since getting it 11 days ago and 80% of that driving has been on Autopilot. In that time it's braked for no reason and approached the edge of its lane while taking a curve. The system is very well done but there is still much more work to be done before it's perfect. It still cannot act as a human would in certain situations.
This pretty much sums up my thoughts as well.
We took a small road trip this weekend with the family (me, wife, 6 year old son, 3 year old daughter, and 2 year old daughter) and I used Autopilot and NOA for 75%+ of the trip.
I've had the car since 4/26 and have about 1,000 miles on it. I've spent a significant amount of those miles testing out autopilot (I'm also a tech enthusiast and this was a big reason I bought the car) so I have a good understanding of when it performs well and when it's going to struggle and I intervene as necessary and always keep my hands on the wheel and my eyes on the road.
This weekend the GPS went crazy on me (posted in another thread with video examples) and that apparently caused some odd autopilot behavior while on the interstate. This is probably the worst thing I've had happen in my time with the car. And even with this glitch I'm very comfortable with autopilot.
My wife has been in a rather traumatic car accident recently and is still very jumpy in cars. Someone T-boned her doing 60+mph and flipped her Audi Q7 with all three kids in the car. Luckily the worst injury was that my middle daughter broke both bones in her left arm. Everyone else was completely unharmed... except the mental trauma that my wife still deals with. Anyway - the reason I say this is to make a point that my wife actually LOVES the M3 autopilot. Sure, sometimes it scares her just like any other human driver would but she takes comfort in the fact that there is a bit of redundancy (autopilot and human oversight) and she loves that I can set the speed limit and just let the car do its thing. If I'm doing the driving then I'll likely go faster than the car on autopilot so she likes the more laid back feeling of autopilot.
On a side note - I know I'm not the first to report this but I AM pleased to say that the M3 comfortably fits 3 car seats. We use Diono Radian car seats and they are fairly narrow (and very safe/substantial - it's the same brand/model that the kids were using in the accident so I'll forever trust them) so if anyone is looking for good, safe car seats that fit 3 across in the M3, these work great.