The Metris, to clarify, has a sensor in the brake pad that, upon detecting wear beyond specification, the computer is notified of that wear, and displays a light and/or dash message telling you that the brakes are so worn, and it will keep showing you that message every start up until you replace the pads. The pads are a high performance compound designed to handle repeated rapid braking from high speed, as one would find on the autobahn. This compound heats slower, cools faster, generates superior overall braking performance, and is less likely to catch fire when the brakes get really hot. Those are its plus points. It has three major negatives: 1) it has substantially shorter life than that of most American and Japanese pads, 2) it has a propensity to both squeak in minor brake applications and grunt loudly just at the minimum point of stop pressure being applied, and 3) It vaporizes under use, causing a dark sticky dust to adhere to the front wheels (and eventually the rears, if you let it go long enough) that is a pain in the tuchus to clean off.
For your increased comfort, Mercedes has been using wear sensors for about 40 years now. Its not new technology to them, and it is quite well proven to be very reliable.
In terms of life, my rears seem to last 30k miles and my fronts 45k. I replaced rear pads at 30k and 60k, and front rotors and pads at 45k. I am still on my original rear rotors. I have somtimes noticed grinding; it sounds similar to the noise ASR makes when active. It hasn’t affected braking performance, however.
Dieter Zetsche, the CEO of Daimler, was once heard to remark: “Germans don’t mind if brakes make noise, so long as they work. Americans don’t care if the brakes work so long as they do not make noise.”
I guess I’m more German than American.