Although I see Mike's point, let me give you some counterpoints. First, this is not another "Pen Windows" of the type that Microsoft brought us in the mid-1990s. Notice that the video shows the woman using her finger, not a stylus. A stylus is just not as convenient as a finger because, well, I always have my fingers close at hand. And, that interface is not Windows. It may be running on top of Windows -- although even that is debatable -- but it's clearly optimized for its device. That wasn't true of Pen Windows.
Microsoft's attempt to move the Windows desktop interface to a handheld device was always a bad idea, but it took the iPhone to show what a good handheld interface might look like. In trying to keep a consistent Windows branding and developer environment for Windows Mobile, they created a miserable user interface. If that video is evidence that Microsoft is willing to break free of the standard Windows user interface, then it's a very hopeful sign.
Finally, Microsoft needs some innovative hardware to create buzz and bring people into its soon-to-open Microsoft Store locations. People can already see plenty of PCs at their local Best Buy, so Microsoft needs something unique, even if it's not something that a lot of people buy. It's not like Microsoft can't or won't build its own hardware. They've got mice, keyboards, XBox, Zune, and Surface, to name a few. So as far as Courier goes, it's not a stretch to think that Microsoft might build something like it.