My bad. I got a corrected invoice in the mail that shows the software upgrade wasn't brake related, but was for the airbag controller. Sorry for the false alarm.

They did a fluid change (not sure if they replaced any parts), but the slow-speed braking is noticably smoother--far less grabby when you make minor pedal adjustments at slow speeds. I was surprised, because it never occurred to me that the service would change anything.