Electric windows opened on their own occasionally when the car was parked. Disabling the "total closure" option seems to have fixed this problem.
Steering joint failed at low mileage. Some cars were recalled due to this problem, but my car was manufactured outside the recall period!
Both front electric window mechanisms have failed.
The car is very large and luxurious. It is also quiet and refined.
It feels very solid and well-built.
It has some very cool features such as
a gradual raising/dimming of the interior lights.
There is plenty of room in the back for lots of luggage and we can fit three kids safely in the back.
The suspension is quite soft which leads to a comfortable ride on smooth, straight roads, but the car gets easily upset on a normal, pot-hole ridden, UK road.
The dealer service seems good, but is very expensive. I am considering using an independent garage purely on cost.
I agree with you about A6 Avant, I have a 2.8 Quattro with all the toys inside. However I have given up on the main Audi dealership. After 90,000 miles my tiptronic gearbox broke, Audi quoted me a price of £5000. After posting my problem on the Audi A6 Uk forum, a helpful chap gave me a number and I got the gearbox from an independent dealership for £1200!
The car though now is a joy to drive, and with a private plate on no one can tell its old and cheap!