I've owned two A8s. One I bought new when the L version first came out in 2000 or 2001. It was a lemon so I sued Audi and got all my money back. I loved driving the car and thought this was an exception so I bought a precertified 1998 A8. Since then I have replaced millions of things. From the transmission (died at 86K) all the engine seals, all the suspension parts, oil cooler twice, fan, heater core (expensive!) etc. I still drive the car since I like it and it is cheaper than buying a new one since I don't like the current body style. I don't have a high opinion of build quality, but it is a great car and gas mileage is pretty good. Use the tiptronic for freeway driving 20% better economy.
look, interior, handling, power
Build it so something doesn't break every 2000 miles.