I own a '23 MYLR which I've had since Feb, no FSD. My wife just bought a '23 M3P that came with FSD for 3 months which just ended. I've run FSD in a combination of highway, suburban, and rural environments. Two things are very clear to me after three months. First, it's performance ranges between excessively timid to suicidal. Second after all the work Tesla engineers have put into this code base, it still doesn't follow some of the most basic rules of the road.
Overall, the level of vigilance and attention required to safely operate in with FSD engaged is significantly in excess of simply driving normally. It's like teaching a first time driver who knows the basic rules (mostly) but is so obviously inexperienced and inconsistent as to require your sub-second intervention. The system is in no way "driver assistance". Rather, it is Tesla product development assistance for those willing to accept the liability and expense of participating. I'm only talking about FSD here. Autopilot, on the other hand, I find to be very useful on the highway.
Summary of FSD behaviors ranging from dangerous to annoying:
1) By far the absolute worst / scariest FSD behavior I experienced was on a 4-lane highway with many at-grade intersections. On multiple occasions while cruising at 65mph in the right lane, the car abruptly attempted to cut right into very short turn lanes. One incident left me with less than a second to recover to avoid the abrupt end of that turn lane and the high-speed swerve required active recovery. (this one is repeatable. FSD will do this every time I pass this intersection). It does this even though the lane is clearly painted with a right turn arrow.
2) Occasional confusion cruising through large, at-grade intersections where FSD seemed to lose track of the lane resulting in abrupt jerk of the wheel left or right.
3) Inexplicable desire of the system to cruise in the passing lane on 4+ lane roads. This one is most annoying because at this point FSD should be best at highway driving. How is it possible that Tesla hasn't figured out that FSD should keep the car in the right lane except as needed to pass slower traffic? Even when I command the car to the right lane with the turn signal, a minute or two later it will try to change to the left lane when I can see faster traffic approaching from behind.
4) (Also an issue with regular AP) The on-ramp acceleration / merge lane swerve. Every time I approach the merge lane the car swerves to 'center' the merged lanes. The car should stick a fixed max distance from the dashed line when on the highway. My Ford with lane keeping and Blue Cruise doesn't do this.
5) FSD fails to initiate the turn signal BEFORE abruptly decelerating for an upcoming turn. FSD signals very late, last 50-100' before the turn regardless of speed. This means the car will abruptly decelerate without a turn signal which could cause a rear-end collision.
6) FSD too tentative at intersections to be used with other traffic present. I get this from a safety perspective, but other drivers don't appreciate a car that stops 10' before a stop sign, then creeps forward before taking off, or jamming on the brakes if cross traffic is detected during the 'creep' phase.
I love both cars for all the regular car stuff they do better than most other cars. However, it's very clear to me that these cars are very far from being truly FSD capable and more than likely lack the sensors necessary to become so. I'm curious if my experience is typical or an outlier.