This "socking away or duplication" of the contents of the iTunes library (same for iPhoto or its successors) was the dealbreaker for me on OS X. It indicated that they were brazenly ignoring the wishes of power users who knew what they were doing, and thus signalled the direction of how the OS would develop.

Good for you for attempting to stop other users getting confused by it -- I have spent several afternoons restoring people's setups for people who are completely unable to organise their files, and explaining this behaviour to them was the dullest part of it.