2015 Audi A8 3.0 TDI quattro review - is it worth the money?

I recently had the chance to get behind the wheel of a 2015 Audi A8 3.0 TDI quattro and I'm now trying to decide if it's worth the hefty price tag. The luxury sedan boasts impressive performance, comfort and features but I'm not sure if it justifies the cost. Your thoughts?