I definately felt going from 40kg of the OEM S3 brakes to the 28kg of my AP 5000+ . Steering felt lighter and more responsive, ride comfort on front increased. As for stopping, it's exactly as Pikey said...you feel no strain on them braking hard from outrageous speeds. Will have to test them better on my next track day to see how RS29 are compared to Carbotech RP2. Until now, I'd say they are not as strong and don't have that "punch in your face" but they are very progressive, make very little noise and work well from cold also !
PS : Anyone knows how important it is to take out the pistons and clean them every 6 months as Ap recommended ? I've heard having no gaskets, dust will accumulate and may damage the pistons ?