Apple? Or some other company whose customers care about it?
While hundreds of millions of people use Microsoft products, and many are happy with those products, few if any relate to Microsoft as an institution they are fond of or care about, or whose products they are excited about.
Microsoft's ineptitude at garnering that kind of relationship with its users is laid out plain in the forced premise and execution of this video.
Why would anyone have a party around the launch of a new Microsoft O/S? I guess it demonstrates Microsoft's confidence that Windows 7 will actually work well out of the box. That would be something to celebrate.