Well, it seems that my first software update has also (seemingly) introduced my first bug. At least, it made it more pronounced.
Whenever I slow down (ex. at a red light), there is a low rumble sound and feeling (shudder, vibration, even) as I hit 4 mph, dropping down to 3 mph, then it's smooth again as I come the rest of the way to a stop. When I accelerate to get going again, there isn't any rumble as I pass that same speed... it's only while slowing down.
But wait, there's more... while slowing down, if I hold just a tiny bit of throttle as it crosses that speed (4 to 3), there isn't any rumble. It rumbles only when I'm completely off the throttle pedal. It's like it's a function of the regeneration or something. At any rate, it just started happening yesterday, after I did the software update. And, I did reboot both screens, by the way, to no effect. I also have regeneration on normal, lane departure warning disabled and creep mode off.
After searching around, I found that I am not alone in this. Some people on the forums are even calling this the "4mph bug." Anyway, several people have mentioned that they talked to Tesla and there's apparently a fix in the works for this known bug. Here's another thread on the issue.
By the way, it really is quite amusing to say that ("bug")... normally we think of cars as having defects or flaws that need to be "repaired" at a service center or dealership. It's nice to know that my car will be "fixed" ("improved," really) without me having to schedule time to take it anywhere or something like that.