Oh I have the manual, it just doesn't specify these things.

I'll try an iPod - thanks all

I know the manual is really (really) annoying, especially in the audio section, but the 2010 manual lists a table on page 4-31.

It says USB supports FAT16 and FAT32 formats, with 8 folder levels of no more than 255 folders and 512 files for nav (dumb) or 8 levels with no more than 999 folders and files without nav (still dumb).

Page 4-61 lists iPod operation, and is really skimpy, but it covers some of this stuff.

OTOH, the 2009 has a CF slot with the same limitations as the USB, so an iPod is really the only option (though I have Christmas music on my CF card).