I dont know for mercedes rotors but i have ceramics on my f150 and my cadillac for some time now..second set on the f150 now and there is negligable to no wear to the rotor, no lip at all i can feel with my finger...Semi metallics wore my rotors quickly in the past....There is basicly no dusting at all.. when i first made the change on the truck i only did the fronts...After two weeks the backs would have noticable red/orange dust i had not ever noticed due to how bad the fronts were before.. front had Now none...Now ceramics all the way around i could not be more pleased with them, and i am hard on brakes in city driving...So i say go for it, that being said i have not had to change the brakes on the 300d yet but they will be getting ceramics if they are available for my car...only negative i have heard about the ceramics is they get your rotors hotter on hard stops..but this has caused me no problems

Again just to be clear i have these on all my other vehicles and damage to the rotors is not an issue at all but i dont know if oem on mercedes is semi metallic or organics if organics maybe the mercedes rotors are softer??

Hopefully some of this long post helps.

Arlo

__________________

W211 E550
HVAC/R Certified Technician