Mmmm.....
I am going to be the odd one out here. I would actually like to see as many as possible people buy run flat tyres .
BMW surely put a lot of thought into this issue. It is one of the reasons the boot space is so big. No spare tyre to take up space. As far as the performance of the tyres is concerned, I think they are well suited to the car. My 320d is a luxury family sedan, not an F1 racing car. I have on occasion put the car through it's paces a bit, and I find the road-holding more than satisfactory. The ride of my E90 is a bit hard, but I can live with that. My first set lasted 48 000 km's. Stock standard Bridge Stone Potenzas.
I bought the car with 17 000 km on the clock, and will be replacing it early next year just before it runs out of MP. This means I will have had to replace tyres once during the time I had it.
Look at it this way:
If you buy a new 320d now, you will fork out roughly R430 000, depending what extras you have. Most people like me, will drive the car for about four years. I those four years you will replace tyres twice, at about R11 000 a pop. So tyres are going to cost you around R22 000 over four years. around 5% of the cost of the car. And you have the luxury of extra boot space, and not having to worry about ever fixing a puncture on the road.
Ok, so let's compare to replacing the tyres with non run flats. You will not be saving R22 000. You will save the difference, namely around half, say R11 000 at most. This over a period of 4 years, while then having to carry a spare, a fix any puncture you have on the road....
So....I guess if you are hell bent playing race-track-driver on public roads, there MAY be an argument for some special high performance tyre...but then...that is not really going to save you a bundle either.
But here is the thing.....one of the reasons run-flat are so expensive, is that not enough people are buying them yet. The cost of production goes up the lower the quantity.Stock holding also plays a role. So if more people buy them, they will eventually become cheaper.
Meh...I guess it is a "personal" thing, but I am fine with the concept of the run-flats. yes, they cost more, but in the big picture compared to the price of the car, considering the advantages, I don't think it is a big deal.