I'm not sure if navigation has much to do with it quite frankly. I have navigation with my 2009 x5 and I find the system as fast as the navigation system in my 2008 M3. Both systems are identical, based on the CIC hardware and have the optional usb/ipod interface. Scrolling long lists is very fast indeed.

Prior to that, I've used the older i-Drive interface (more colours) and first generation ipod interface. That system seemed to be very slow to react and scrolling long lists was painfully slow.