Sorry for the delay in responding. Yes they do remove the crashy ride, but only to a certain extent. Don't forget you are still riding round on 40 profile tyres (35 rear), but the ride is much improved. Not spoken to anyone yet who has changed that regretted doing so.
My other issue with run-flats is that I had a puncture on a rear, and the car drove pretty well. So much so I didn't notice it was punctured. Was only when I gave it the beans off a roundabout that the back end squirelled a bit and the traction control came on. Tyre looked ok from visual inspection, was only when I put a guage on it that I knew it was way down on pressure.
Result is that it destroyed the tyre side wall, and it possibly could have been repaired (yes I know they say you can't). This was when I started looking at the standard tyres.
Bought myself a BMW tyre inflation kit (pump & tyre goo) just in case the worst should happen!