When the iPhone was being announced, I thought "Good, Apple will do something unique in handheld UIs."
Instead, they put out a 1984 style icon grid, with a bunch of non-integrated standalone apps. Big whoop. All the other stuff was old hat to us enterprise touch screen folk. Granted, it's a good choice if you want to keep things super simple.
Since then, I've waited for someone to take a truly fresh approach. Palm and HTC started the idea of integrating all social pieces together, but didn't take it very far.
Now Microsoft steps with in a far younger generation of UI designers, who understand that a lot of people will want things grouped by social activity. It won't be the UI for everyone, not by a long shot, but at least it's truly innovative.
Apple cannot afford to do anything like this, because it doesn't hit as many tiers of users as they like. And frankly, I think Apple is stuck because Jobs had a hit with the original Mac and still thinks icon grids and single-tasking are sufficient.
I fought Microsoft most of my professional life. Unlike some of the loudmouth kids around here, I actually invested a lot of time and development and money in trying to create and boost competing products, probably while many were in diapers. But I have to admit, I'm pleasantly surprised that MS's old guys let go enough to let this kind of UI get attempted.