Using the new controls is pretty simple. When in Traffic-Aware Cruise Control mode, you just roll the right-hand scroll button up or down to adjust your speed. To change the distance between you and the car ahead, push the right button to the left or the right. "You can still adjust these settings from the touchscreen and press down on the button to activate voice commands," Tesla adds in the 2018.12 update notes.
Engadget's Roberto Baldwin specifically complained about the lack of physical adjustments for cruise speed and follow distance. "On the Model 3 you have to tap the display to adjust the cruise control speed," he noted. "Even worse, you have to go into a submenu to adjust the adaptive cruise control follow distance." That not only removes driver attention from the road, but makes it easy to tap the wrong function if there's a bump in the road.
The new software also addresses another of our complaints, letting you adjust the side mirrors using those same buttons (though you first have to select the items from the screen). All of those things are crucial on the road, so Tesla seems to be focusing on safety first while adding physical control functionality.
As we also noted in our review, Tesla's unique ability to add new functionality via software updates can completely change an EV's utility over the course of months or years. That especially applies to the Model 3, which depends more on technology than the other models.