Firewire.
Reading through these quotes SvN gathered from a macrumors thread when the iPod was first announced, it became quite clear. I had two MP3 players before my first iPod and loading music took far too long. The price was fine and it held more albums than a CD, so you'd think they were in like Flint. Well, as you've probably heard before, it's the experience, stupid.
The iPod+iTunes combination blew everything out of the water. Looking over an old post, It's probably that put my fully back in the Apple camp.