I have had several BMW models with run flats that I have had the 'opportunity' to drive while actually flat.
2006 Z4 Coupe E86 Sport Package: Terrible tires, noisy and made the handling and ride awful. Had two occasions when the tires got nails (both in the rear). Could not tell the difference on normal roads. Noise etc. did not change at max allowable speeds. Bridgestone. Replaced with Michelin Pilot Super Sport RFT which helped dramatically with noise and ride but handling became suspect.
2007 530i E60 Sport Package: Excellent experience. Quiet with no issues for handling or ride quality. Two punctures. Again the car rode and handled on normal roads without a problem at max allowable speed. Drove safely to dealership in one case and Discount Tire the other time. Repaired once, replaced the second time since they were also worn. Continental
2012 528i F10 MSPort Package: Tires are noisy. Handling fine. Ride slightly uncomfortable (not smooth) but improve as they warm up. Puncture in rear right tire. Replaced under tire warranty/protection by dealer. Drove safely to dealership no issues. Noise and handling changes undetectable at max allowable speed on normal roads. Continental.
2012 528i MSport, Space Grey, Black Dakota Leather, Nav, Premium, Heated Seats
2013 X1 XDrive 28i Msport, Valencia Orange, Sand Beige Nevada Leather, Ultimate, Lighting, HK Sound