Just took a short drive on local roads (35MPH speed limit) and AP seems to have improved in initiating the braking process earlier and more smoothly when traffic ahead is stopped at a light. Also, the acceleration seems to happen more quickly when the traffic ahead begins to move after stopping. I still need to use the accelerator pedal to keep up, although it's needed less than before.
I haven't experienced any issues yet, but I wonder what's going on with the minimal number of installs for 40.1 on TeslaFi (11 yesterday and only 5 so far today), while 36.5 (currently 462) and 36.6 (currently 903) have ramped back up.