I don't get it. Most of what iCloud does is already being done on smartphones for free. Gmail and Exchange Server both already sync contacts, calendars, and email quite nicely across devices. I haven't had to manually transfer any of that to a new smartphone since long before there was an iPhone. The music thing is nice too, but it's either a paid solution or an incomplete one. Apple once released a stat that only 10…
The key differentiating factor is that the iCloud heralds an era wherein all of your data is decentralized, all of the time, and that this is the default for all users, on all Apple devices, all of the time.
You are correct, for all definitions of "decentralized" that are "rigidly centralized, almost appearing decentralized because centralization is so far outside your control"