stress tested the adaptive cruise control
 

for abt 3k miles on the thxgiving trip. I disengaged/engage the cruise control, setting new speed, adjust distance many many times to account for different road conditions.

a few observations:
it brakes abruptly when car cuts in.
it brakes abruptly when car in front slows down
it accelerates fast when it senses a big gap in front.
it needs some gas to move from a red light
...

overall: helps with long distance driving a lot. But in certain cases human driver is better to maintain a smooth ride for passengers. Also human reacts to conditions earlier and predict better.

And also, it often "rides the brakes" going down-hill so as not to exceed the speed you set. For me, I don't use ACC going down hills, I just use the paddle shifters to keep my speed where I want it.

I think if you go to the MMI and put in "Comfort" settings it will not react so abruptly, especially acceleration.

The ACC settings in the MMI adjust the rate of speed at which the car will adjust to distance changes of the followed car based on your distance setting on the ACC stalk. In other words for example, the "Comfort" setting will cause the car to react more slowly to maintain the preset distance.

Couple other observations...
1 in slushy snow the front bumper becomes covered and the speed control quits working as the sensor becomes blocked.
2 even with the distance set to closest setting, it seems like you need to start passing a car in front moving slower much further away than you otherwise would.
I wish there was a way to override the ACC and have the option for old fashioned cruise control. Most of the time if works pretty good, but it seems like it
takes more adjusting in heavier traffic than "dumb" cruise control.

Some additional comments...

Putting the car in Economic Mode will extend the distance a bit, to offer lower fuel consumption.

Yes, pushing the throttle a bit will re-engage the ACC, but you can also engage it from the lever itself by pulling it towards yourself.

Unfortunately you are another poster who does not include their location in their posting. I say that because you mention the "Economy" mode and my car only has it because I enabled it via VCDS. I do not use Economy because of 1. - I think that it created some fault codes when used with Chipwerke and 2. - I bought a sports sedan and economy is not its reason to be.

I have also programmed the ACC to hold on for about 10 seconds after the initial release after 2 seconds but I wish that it would never release at all without driver intervention.

I also think that the take off when following a car from rest is useless and creates too much honking from the cars behind you. I am trying to program some changes in that too.

Otherwise, I use the ACC for at least 80% of the 18000 miles that I have driven my A6. I maybe the heaviest user of ACC on this forum.

A simple light press of the accelerator gets the car going immediately from a stop. Not really a big deal (unless you are mssing a right leg).

"Otherwise, I use the ACC for at least 80% of the 18000 miles that I have driven my A6."

I also use ACC most of the time. About the only time I don't use it is when coming down steeper-hills, or when the Highway goes up and down when my brakes would come on (otherwise I would coast up 1-2mph above the set speed) spooking out the driver behind me. I've always used "Cruise Control", even on my Motorcycle, so I can maintain the speed I want and don't find myself well over the speed limit.

Or a pull on the cruise control stalk will achieve the same function.

If it requires driver intervention from the pedal or the stalk then it's not "automatic", my automatic gearbox does not require me to push/pull the stick shifter.

With a mod via VCDS, you can pre-arm the ACC so that you don't have to intervene at start off.