Little interior crap breaks all the freaking time, nothing too major. The trunk hinges, trunk motor, and trunk pull down motor all have issues.
One of the major problems your gonna have is the upper control arm links, they use the same size bushing as an
A6 but they use a larger link. The problem with this is the
A8 is a lot heavier and tends to beat the living **** out of the bushing to the point where the links start floating around hitting the strut tower.
I see them have a complete failure at about 40k. Chances are the
A8 your looking at has shot ones already. Repair cost for this you ask? $600+ for the links and about $400 in labor. Un-less your one hell of a mechanic and loves to swear, these links aren't as easy to replace as an
A4 or
A6.
Other than that crappy problem.... the air suspension seems to hold up nicely, oil changes suck on a D3
A8, and the MMI screen motor gets jammed a lot which is another pretty costly repair.
Overall if you have the money and don't mind paying the price for the repairs on it, get it. It is hands down the most luxurious and comfortable car i have ever driven (including very pricey mercedes) and i would recommend it to anyone that want's the best money can buy. But like i said, if you don't have the money to repair the sucker it will be a headache and a nightmare.