I think the real direction will be dockable I-Pod-like devices. (The I-pod seems perfect in scale and form for just this). These devices are likely to be adopted by the very-same people that adopt the I-pod. And, as we have all seen, even execu-techno-phobes are starting to use the I-pod.

If you created a DIN sized deck, with CD and FM and a "docking slot" for an I-pod - you are there. A full-featured stereo, with CD and radio, that becomes a 5,000 song jukebox. You rip ONCE into the I-podish thing, and you can use it as a portable.

Cheaper versions could use just a "USB Caddy" which is not a player in its own right, but simply a portable HD.

Of course, the display and UI will be the life or death of ANY new MP3 product, particularly the car unit. Empeg is very close to ideal, with some mods it could be pretty damn perfect.

Just my $0.02