The Secret Ingredient

The Zune is the most recent example of what other companies, and even some reviewers, don't understand about the iPod and its unrivaled success. It's not just the pretty hardware or cool commercials, it's that Apple, more than anyone else, understands that complexity for the sake of complexity is a terrible thing for consumers.
When you buy a product you don't want a manual as thick as a copy of Gone With the Wind, or a system so complex it requires an engineering degree and a particular ear for acronyms to make it work. What consumers want is a device that does what it's designed to do with a minimum of fuss.
Apple understands this. They may not always be successful in making this a reality, but with the iPod they've made a sincere attempt to make a great technology.

C|Net has an article penned by their executive editor of commentary about this very issue. Titled "Why It's Hard Not to be a Grinch," the article describes the author's frustration with a SanDisk Sansa m240:

I won't bore you with the details of the software hell I suffered, but there were any number of minor technical questions the company leaves customers to figure out on their own. Lincoln's Gettysburg Address is longer than the tiny booklet of "technical documentation" that came with the unit. Three pages of instruction–-in big type-–in three different languages just didn't do it. So my frustration grew as the afternoon lengthened into the late evening and still I was left trying to understand the particular mindset of the genius who designed the music player's interface.

The iPod just works, and that's why is currently the king of the Mp3-player market. The sooner SanDisk, Microsoft, and others figure this out, the more meaning all those extras like WiFi-sharing will have.

Link.