There were quite a few programs that synced iTunes playlists to non-Apple phones. This supports your assertion that people were dependent on iTunes for library

There were quite a few programs that synced iTunes playlists to non-Apple phones. This supports your assertion that people were dependent on iTunes for library management, but not that there was lock-in to Apple hardware. I feel that it was the seamless ease of iTunes/iPod/iPhone that won, rather than a hard moat.