The people who say iCloud is a music locker are wrong. The people who say iCloud is a rebranding of MobileMe are also wrong.
They’re thinking too small.
If the USB port was essential to Apple’s Digital Hub strategy, then iCloud will be the fulcrum of their Post-PC strategy. It will sync everything, including your music collection and app metadata. Developers will be able to use an iCloud API to keep their apps in sync across iPhones and iPads. Users will be able to keep an iWork document in sync across every Apple device they own.
But more importantly, iCloud will bridge the gap between iOS and Mac OS X. Monday’s keynote will be the most important in years.