it's been a problem for almost all the car mags that tested the rs6
they all complained that the brakes weren't up to the job of stopping the car consistently after some high speed runs

there was a write up in top gear where they set fire to the brakes too

so i'd say mike was right in his thinking about the pads, but if you go for pads that don't catch fire, you have to go with the limited lifetime of the components