My wife has a 09 750Li that we picked up in Oct. I've only driven the car 3-4x and have been disappointed with the ride and stupid e-throttle/transmission every time. I noticed a slight vibration going down the road at 50-60 today and attributed it to the run flats but after reading this thread I'm not so sure. Having had a 03 745Li, I can tell you this 09 doesn't ride nearly as nice as my old 7. Is it possible the rear wheel steering is contributing to the problem? Maybe alignment shifts under load and makes the rear end squirrely within a certain speed range? It would explain the seat of the pants feel vs steering wheel shimmy.
2008 911 Turbo
2009 Escalade ESV