I received the FSD (Supervised) 12.4.3 update last night and had my first drive to work with it this morning. I didn't have to touch the steering wheel at all, which was amazing. I also noticed that it didn't change lanes like a NASCAR driver, which was my biggest gripe with 12.4.1. The morning was a bit rainy today and I noticed that it was consistently driving 5-6 mph under the speed limit and that it slowed down for turns much more than previously. Was this because of the rain, or a core behavior of this new version? Time will tell, and I'll update here.
Edit:
The drive home was in full sunshine. FSD 12.4.3 continued to drive 5-10 mph under the speed limit. It was a very frustrating drive home with lots of accelerator petal presses to encourage the Tesla to drive at least the speed limit. This happened after every light, turn, or braking event for a car turning in front of me. Lane changes continued to be minimal, but to the point that it missed a getting over into the turn lane on a busy road in rush hour, completely missing the turn. It waited until about 50 yards before the light to start signaling when it should have (and has in previous versions) gotten into that turn lane 1-2 blocks back.
Since I've gotten home, I have rebooted the car by holding in both scroll wheels and cleaned off the cameras (which did not seem dirty.) Hopefully, a fresh start tomorrow will have better luck, but I'm beginning to think this version is a major regression in all aspects except for acceleration/deceleration and less aggressive lane changes.
2nd Edit:
It found that the FSD profile was set to Chill. Once I bumped that up to Average or Assertive, the 5-10 mph under the speed limit was resolved. In the past I've been hard-pressed to notice a difference between the different FSD profiles, so this was a surprise. It still feels like lane selection still needs some work. It is waiting too long to move into the correct lanes to make the appropriate turns when navigating.