I have bought the OEM iPod adapter accessory and it is fully functional, menu is displayed, iDrive controls and the cable charges the iPod.
6FL USB is a factory option, cannot be ordered after the car has been delivered - this iPod adapter can be ordered instead.
The only limitation is the lack of connectivity with other USB devices, such as pen drives (it comes with the iPod proprietary connector)

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X5 3.0d - Space Grey , Beige Leather, Burl Walnut Trim, SatNav, Rear Camera, Sunroof, Light Package, 19" 212 Wheels, Tint, Power Fold-in Mirrors. AUDIO: Morel Elate 6 Audiophile Speaker System with Genesis Dual Mono Amp and Rockford Fosgate 3Sixty.2 DSP