I have spent quite some time evaluating the current situation of iPod integration capabilities of various car hifi products. And the result? Most manufacturers that brag about iPod compatible head units offer terrible capabilities, most of which were mentioned in other posts (lack of control, only a few (6-10) visible directories
...). This manufacturer shitlist includes names like Sony, Blaupunkt, Kenwood, Pioneer and VDO.
According to a very good car hifi dealership in my neighborhood Alpine and Becker are two of the few that offer great quality of iPod integration (all data visible, freat control and integration ...)