I actually think the problem is that they are run flats, as they get a bit of a bad press. The sidewalls are really stiff and corrupt the ride quality. There's a reason why M-Division BMWs don't have them but the rest of the range do.
However, having had a front puncture in my Mini Cooper S at 85 (on a private road) I was delighted to be running on run flats. There was no drama at all and I just carried on my journey at reduced speed. A blow out could have been rather more exciting.....