I had RF on my R55s. The summer ones were ok (Continentals), but I really enjoyed the car more when I went to non RF. The ride was smoother and I felt more connected to the road. In the winter I ran RF Dunlop wintersport tires and I liked them a lot. Great in the cold and snow and built for high speed. I suppose that winter is the best reason to have a RF as you just don't want to think of changing or repairing a flat in the deep cold, slushy wetness that is Canada.
So the F56 came with RF Pirellis, I feel that they are a vast improvement over the early generation of run flats. Not nearly as hard feeling and the do feel connected to the road. I've done some spirited driving and these have not let me down. A weakness might be the grip in the rain, not as good as my previous Bridgestone RE 760 tires. Part of the better drive with the Pirellis must be that the suspension is set up for run flats and the F56 in my mind has a much better suspension then that of the R55. I am currently looking for a winter set and I will go with the latest generation of Blizzak run flats, for the reasons above.
Ok, so if you get a flat, it sucks, these are expensive tires. My recommendation is; don't buy them at the dealers. I found that my dealer was easily, 20 - 30% more than what a tire discounter charged and let's face it, almost any garage can mount a tire.
So for safety (imagine a blowout when you're carving a monster corner at speed) and for convenience (stuck at the side of the road in an ice storm) you can't beat a run flat tire. The question is, do you want to pay a premium for that. I do.