I came across some vague technical document on the web - which was probably obsolete - that it's a direct connection to whatever black box handles "entertainment."

Page 188 of the manual (well, the 2011 X5 manual anyway) says it is the ONLY way to transfer music from a USB device to the vehicle's hard drive.

The rest is quoted verbatim..

"Suitable devices: USB mass storage devices, such as USB flash drives or MP3 players with a USB interface."

"Unsuitable devices: USB hard drives, USB hubs, USB memory card readers with multiple inserts, Apple iPod / iPhone."

"Music from a USB device can be stored only via the USB interface in the glove compartment."

OK, so that's what it's FOR: COPYING music from a USB memory stick onto the vehicle hard drive. Why you would do this? I dunno.. It might be easier for some folks? I'm OK with flexible, even if I don't use it.

The one in the center console is for everything else, and you can play music from anything there: USB memory stick, hard drive, iPod / iPhone. It also can charge the device.