Picked up our Z4 yesterday

and used the recommended iTunesExport tool to transfer a group of play lists and associated audio files from our iTunes library onto a USB drive.
http://www.ericdaugherty.com/dev/itunesexport/
The USB drive I used for this was a Corsair 32GB Flash Voyager GTR USB Flash Drive. (Incidentally, I did also try a larger 64GB low power 2.5" SSD drive, but the system indicated that this wasn't supported when I tried to select it.)
The settings I used in iTunesExport were as below
Everything works really well, with the play lists, artists, album details all available for search and selection.
One point to note is that it takes the iDrive system a minute or so to read and index the files on the USB drive, I first of all thought that the process didn't work, but after a couple of minutes all the selection and search features were available.
Great system, much better than the Command system that we had in our 2008 CLS.
Steve.