My favourite addition is ACC/DCC. It is brilliant as the car's dynamics can match one's mood so effectively.
If I may, I disagree with Ess_Three that the car tends to float in 'comfort' mode. This could be misconstrued for that 'big car feel' which it certainly has in this mode.
Round town, in 30 MPH limits, there are no issues.
But forget to turn it off, and try a decent twisty back road...and it feels like a 1980s Merc...wallowing and flopping all over the place.
Big car feel indeed...

At low speeds I notice no issues, or at higher speeds on motorways...it's just not suited to throwing the car down a challenging backroad....but why would you want to in 'Comfort' anyway?
Isn't that what 'Sport' is for.
Regardless, I wasn't sure how much the character of the car would change in each mode...and when new with non-run in dampers, it was hard to tell.
Now though, there are 3 distinct sets of behaviour.
Well worth the cash in my view.