This new flap before or on the side of the tire looks interesting.
I think that the underside is where they have made their most gains in CD. Also if your cars underside is well designed it does not make any harm to push air also there. If you have very sharp lip on the spoiler there will be turbulece right under it. In my opinion the MB has enough smoothness in their bellypan. It creates similar venturi reaction that in sports cars and accelerates air flow...
Notes on the outer side that is best video I could find because its "slow motion":
- Front bumber directs the air slightly pass the front tire. Same on the rear tire
- Front side panel is slighly more inner than front tires outer rear edge
- On rear tire the rear bumber has about that 10 degree slope and its designed so that it will go about tangent rear tires outer edge.
- Rims are quite aerodynamic with little bit of covex shape in them.
- I believe mirrors are the same as in E class. Design them good in one car and you can use them in other similar models.
- And the most important feature that template C roofline like ChazInMT pointed out.