you have to start with this : Audi makes money with or without the extended warranty, it is not at all a gift
the option is based on the following : if you take it, your money is already at Audi from day 1, and what you bought is just peace of mind. You have 2 years to see if you got a good or a bad car, and if it is a bad one, resell it. If you don't take the extended warranty, you'll pay all the bills, but it is not sure it will be more. Here also it a case of good or bad luck. I would only take it if I 'm afraid not to be able to pay a large bill. Audi wins in both cases : if you take it, they have the $$$ (based on customer prices) and what they give is time and furnitures at their own lower cost price. If you don't take it, you will have no warranty favors after the first two years (even not a day after...) and they will charge the full price for later
my experience : my former A4 had zero problem up to the 4th year, but the bills increased after the 5th.
I'll replace my Q5 in 2014... and I've no extended warranty