ACC is an option that relates to the type of driving your into & type of roadway travelled on.
My last MK5 GTI with KW V3 coilovers and small H&R solid sway bars was fantastic on the Pacific Hwy from Sydney to Gold Coast. Nice smooth freeways were the go for the KW variants. On the other hand, the ride in Sydney Metro and along the New England Hwy through inland NSW cities such as Tamworth, Armidale and Warrick was a bit punishing. Esp with aftermarket sway bars. Just too firm, even with the KW V3 compression and rebound rates set on almost full soft.
ACC is going to allow for softer on New England Hwy and harder on Pacific Hwy. The damping rates may only be subtle, but that's all that would be required imo after test drives on the non-ACC Mark 6 GTI on 17" Denver. Firm suspension is a beatch at lower speeds, but the ride improves as speed rises. Like the GTI's fuel economy, even when under the pump, I like to have my cake and eat it too.
I also felt that an innner city drive along New South Head Road twisties had me wanting a greater level of damping, only about 10-15%, nothing copious. This was in the city at the lower city speed limit. That is damping towards the harder sport setting. Very rarely around town did I opt for any more comfort on the stock non ACC 17" wheeled GTI.
The springs and sway bars in the GTI are well sorted for everyday use, its only the damping that I change in certain conditions. In terms of ride height, imo the GTI sits well low enough, esp with occupant(s) on board with the 18" Detriots.
The reason, I think, that the DSG version of the GTI has firmer front springs is to compensate for the added 20kg of the DSG gearbox.
I had ACC as a definite option with a mind towards handling and usability. I later added Bi-Xenons for a similar reason. Helps stringing corners together at night, making for a less taxing drive and a safer drive, depsite costing about 1K to replace.
I also later added park assist, as rear only sensors would cost @$800 + RVC $500 bringing up the price up to @ $1300. Rear only sensors do not offer the auto-dipping mirror on the Mark 6 GTI, as it's a dealer fitted option for the sensors.
Park Assist with front and rear sensors & auto-dipping left mirror was $1400, so park assist it was (dealer manager later told me RVC was only available with SATNAV, which was contrary to what the salesman told me & incorrect) ... it was a no brainer.
I can park a vehicle like I can manually change television channels by getting up off my butt & pushing the buttons. Front & rear sensors & auto-dipping left mirror is bit like your TV remote control ... less effort involved for the same result.
I'd gladly trade Leather Upolstry for ACC and Park Assist.
Cheers.
WJ