Michael made the point that Microsoft tried to do something innovative and forward thinking.
I think that's misplaced.
I don't think there's a need for the same interface on my phone, my tablet, my TV, and my laptop. In fact, I think the world is a much better place when all of these are different.
I'm (mostly) taking time off in Las Vegas for a few days. But I went to a small digital signage show yesterday. The coolest product I saw was the Bright Sign hardware. They are part of the Roku family so they care more about pushing hardware units than they do about what you run on their hardware.
Their basic interface is simply HTML 5 objects. See www.brightsign.biz. With that, you can create interactive menus, games, etc. There are dozens of examples of interactive interfaces created with their product.
On a similar vein, the iPad is flexible in a million places because of the simple and obvious usability of it's interface. The Kindle is popular and addictive because of it's excellent interface. The Android phone has taken over the world because of a very usable interface. Whatever Android hasn't take over is taken over by iPhone and Samsung - because of the interfaces.
And Windows desktop (Windows 7. Windows XP) completely dominates the world of business because it is easy and usable.
My point is: There is not ONE perfect interface for everything. I don't think there ever will be. I don't think that it's really even a good idea or a noble goal. There should be many different interfaces. Let each interface find success in the right product.
The only real argument for having a single unified interface is world domination. If you could create an interface so amazing and spectacular that it was the ONE right interface for tablets and phones and TVs and laptops and desktops, then everyone would love you and everyone would buy all of your stuff and no one would ever buy anything else.
... And you could never change it. Revving from one version to the next would have to be rolled out over years.
I think it is far more creative and innovative to have a different interface for each product. When a component (e.g., swiping with your finger) is clearly a better way of doing things, then everyone will integrate that.
And as new devices come into existence, new interfaces will come into existence. And maybe many common elements will be reused. But there will always be much great innovation and creativity without a unified interface than there would be with a unified interface.
So Microsoft needs a new plan.
"What do you want to do tonight, Satya?"
"Same thing we do every night: Plan to take over the world."