Purely on the basis of this article...
1. The home page can only work in portrait, is that right? Does everything else need landscape? Oh, and it looks crap.
2. UI's bigger than the screen? Tricky one this - it's ok for data to be bigger than the screen, but the UI? Could so easily go wrong.
3. MS lock in (outlook, exchange, xbox, and I'll bet Bing)- sorry, that's a fail. At least facebook is on there, but hopefully these can all be changed (inc facebook)?
4. Apps that are more than apps. Ok, this sounds clever, but one thing that the seperate app theme google/apple use is at least intuiative - I can see this MS version getting abused, and becoming counter-intuiative.
On the whole - looks pretty enough (home page excluded), in a noughties-London-graphic-designer type of way. That doesn't necessarily mean "practical" though.
Apple and Google don't need to worry too much, IMO.
Author has a point about ios' notification - yeah, the count above an icon (eg email, calls, txts etc) does work, but frankly it can be done better, surely. What about integrating them onto the "unlock" screen?