Our X3 has a distinct wind noise above 40-42 MPH. It sounds as though it is coming from the driver side door/window area. I suppose it could be the mirror. Not sure.
I do LOVE the X3. I don't regret buying it over the Q5. But WITH 20/20 hindsight, had I been forced to take a 2013 with Start/Stop and the noise, I would have settled for the Q5. The X3 is a LITTLE high strung for highway cruising. I think it is a combination of the run flats and the Wind noise. I guess I just want it all, comfort (quiet) and sport. When spending 50K + I would think I could get this.
This is my first BMW, and it won't be my last, but I don't see myself buying a car with Start/Stop. So it will likely be older BMW's or V8's...
Why BMW can't offer Start/Stop defeat as option or extra cost options is beyond me. I hope Dinan or someone figures out how to make the feature work on demand instead of on by default.