Mike, it is there for some time and it is a very practical feature (was there for ages as simple light fitted either in the mirror or in the door, but logo works as well). I drive GLE 450 and there it came together with some package, I did not order it separately. To me it may look like a "posh" gadget, but it is very practical. It is also a topic to make fun when you are with friends at the car door.
What was optional was the grille logo illuminated. I did not order it.
As for the new Mercedes cars - I use only this brand. I had a privilege in my life to drive quite a few cars new, various brands (Fiatx2, VW, Opelx2, Skoda, Ford, Saab, Jeep, Volvox2, BMWx2, Mercedesx4). The only two brands I did not have any issue with within the first 3 years were Saab and Mercedes. The rest was just close to junk, sorry to say, maybe with some positives for Jeep (with Daimler V6 engine, but the tail gate was breaking down all the time). Saab is gone, sadly. I bought altogether 4 Mercedes cars new and 2 second hand from the dealer for my daughter. Never ever anything happened to them. When I looked at A180 from 2011 that I bought for my daughter as the first car from beneath, on the stand, when the covers were removed, it looked like factory new - no rust anywhere (we do have salt in the winter).
Also: having a Commercial background - I value what the brand stands for. I think it is important if the brand is pretending to be something else or not. VW is what it promises (putting aside criminal character of VAG organization). Skoda is what it stands for. Audi - pretends to be premium (crossed from my favourite brands list), Volvo pretends to be premium and safest. Jeep is super honest - I love it as a brand. Mercedes also is what it is claiming to be.