I've had 5 BMWs, the most recent a 530i. I really, really enjoyed driving them, was active in the KC owner's club, drove them on road courses during driving schools, and I had a wonderful independent mechanic which I learned was imperative in keeping them humming at a reasonable cost.
Our local BMW (and Audi, Volkswagon, and Cadillac) dealer's business plan was not to stock parts and let the KC dealers floorplan his parts department for him. I'm sure it was a nice gig while he was getting away with it. When KC got wise to him, they quit sending parts for his repairs. When I was using this dealer, I'd take it in for diagnosis, get sent home and they'd call me back when the parts were in and that was usually 2 - 3 days later. It got to the point of even catching them lying to me about having a part I knew was needed in stock and then being told it had to be ordered.
I found this independent mechanic when his father-in-law stopped me one day to tell me about him specializing in BMWs, I gave him a try, and after a short time, we became friends and he was my trusted auto advisor. He had a decent inventory of parts so I was usually in and out on one trip. He moved to run a service center in Georgia and I couldn't find a new mechanic locally I trusted. I haven't owned a BMW since.
Moral of the story? The mechanic is the one who 'ultimately' makes or breaks your overall 'driving experience'.