It promises a lot: ultimate, seamless connectivity for all devices, cameras, PCs, smartphones, even Macs. Unfortunately at the moment that's all it is, promises.
I have been given access to a special invitation preview, that I've signed up for but hasn't yet yielded an account. From what I can make out though, at the moment all it is is file storage. Put some files in the cloud and access them later. useful, but not ground-breaking.
Now, I know there is more than that to come, but at the moment that's it. It feels to me like a rushed announcement before the ink is dry on chapter 1 of the Live Mesh novel. I'd expect to at least get to the end of the first act.