Second try, I navigated to a Costco south of downtown Seattle from home, about 11.5 miles. This time, the vehicle kept to its lane instead of straying over the double-yellow line near the start of the drive. I made it to Costco without an intervention, the drive went very well, and 12.3.4 did very well in the Costco parking lot with other cars and pedestrians. One person stepped in front of me (I had my foot over the brake pedal), and it stopped at a reasonable distance from the crossing pedestrian. I thought about trying to do an autopark and decided not to push my luck today.
On the way, I noted that FSD now signals for mergers onto a freeway from an onramp. It also recognized a speed limit change approaching a bridge that no earlier version every recognized. It did a good job changing lanes to the right lane to make a right turn after the bridge onto a city street, but it didn't signal when it made the slight right turn onto the street.
On the way back from Costco, I had to intervene in the parking lot when my vehicle approached a stopped vehicle ahead of me and didn't seem to stop fast enough. I stopped it myself. I did have a phantom braking event on a freeway on the way home.
A BIG ISSUE: This version does not seem to see orange traffic barrels. In V11 and before, barrels appeared as orange traffic cones. Also, there were orange posts along a bridge where the right lane was blocked off, and those orange posts were not imaged. Perhaps tomorrow I'll go back to the construction zone with the barrels and drive in the right lane that gets closed by the barrels and see if the vehicle responds to them but doesn't display them.
One thing I don't like is the speed surge after a right or left turn. It's not necessary to accelerate so aggressively. I hope that gets fixed shortly.
More testing tomorrow with scenarios that V11 consistently failed around here.