In any design project, there are two elements to the product. You have the essential elements and the non-essential elements. Both aspects have different things that make them attractive.
I read the Wikipedia page on Chris Bangle, the designer responsible for some of BMW's more bizarre design decisions of the last decade, and got to thinking about criticisms of him and his work.
I think a lot of the criticism might stem from Bangle's ostensible arrogance. After creating the Z4, he announced that they had advanced beyond Frank Gehry's Guggenheim Bilbao. More than a few people disagreed. I wasn't well-versed enough in design to really talk about it, but that didn't stop me. I thought the Z4 was hideous.
And yet, the Z4, and the 6-Series and 5-Series have aged very well. Many of the details that looked so bizarre at the time now look absolutely pedestrian, and the cars simply look alright. That was the thing, after I realized it, that showed that Bangle and Hooydonk, the other head designer, were actually very skilled. The cars aged well.
The fundamental elements of each car are incredibly solid. The proportions are absolutely perfect, and the necessary lines of the car, from the headlights to the A-pillar, the belt line that flows from the front to the back, and the proportions of the body to the height of greenhouse are all excellent. That strong foundation allows us to become used to the non-essential elements, like the 5-series headlights, and accept them as character details to an otherwise firmly designed car.
Bangle has discussed how he wants to change automotive design entirely, but he's not so pie-in-the-sky as he may want us to think. His designs played with details more than with the foundations of the cars. The Z4 is muscular and looks ready to pounce. The 6-Series is long and smooth, like it's relaxing on the road. His basic designs are rooted in long-established norms of aesthetic appeal.
Perhaps his great achievement is what he wanted all along. He got us used to wild and wacky details while supporting them with an almost invisible foundation that is classically beautiful. Cars are still cars, but they look much better, and, perhaps, we'll be more open to strange car formats that wouldn't have been accepted a few years ago, like the new 5-Series GT.