I have some stuff I listen to privately. I keep that in my local iTunes library, synced with my iPad and iPhone.
I got so fed up with iTunes for my DJ stuff, that I stopped using it for that altogether recently. Until then I had it on my external disk. Just a small, no external power, 2,5″ thingie. And yep, I’d plug it in if I was somewhere for a longer period of time and wanted something other than my “limited” 30GB personal collection. The HD fit easily into my laptop bag. Just don’t leave a USB port connected when you put away your laptop. USB has a tendency to break off (both on the laptop as on the HD side, I speak from experience).
Greetinx,
C.