How does this differ from DropBox, which has been around for several years, enables private storage, sharing peer to peer with prior user approval and provides notification of modification to all users, or entirely public files?
DropBox is available for free to anyone, no need for Windows 8. Works just fine on XP, icon right on the desktop if you want.
DropBox is awesome; automatic backups to the cloud, auto sync to multiple devices, and automatic versioning of every document saved. This has saved me numerous times where I revised a document, didn’t like the result, and simply recovered an earlier version from a prior day.
Essentially, not very different, except MS has integrated Skydrive into the OS and Office now, making it seemless. No dragging and dropping....just save the file where you want.
Also, with my Windows Phone, every picture I take is automatically uploaded to Skydrive and instantly available on my tablet without my having to do anything.