Remember ordinary users will like n use most of the OSes that MS will launch. MS people are not stupid about their business. They will not launch a thing that will be rejected by people in masses.
IMO it,s a clever idea to use two interfaces that are inter-changable. If windows tablets supported a wide range of hardware and peripherals like windows PC then I have no doubt that they will become a serious rival against iPad.
Inf act if both interfaces existed in same version and are inter-changable acc to user,s wish, it might be a major breakthrough. MS will put classic interface by default on desktops, laptops and netbooks and tiled interface in tablets/ slates. On top of this, users will be able to change it either way they want, on both the desktops/ laptops and tablets. I don,t know of any other OS in the wild that gives users such an incredible option. Still more to this- if you see the video you can notice that classic interface is running right underneath the tiled interface and it seems very easy to access files/ folders in the manner we access them in windows classic explorer. That is another great option non-existant in rival OSes( android n iOS). I suspect if they used same interface options, in the future, we will see every other laptop/ netbook coming with a touch screen, so that it can be used as a tablet if the user likes so. I have even seen touch screen laptops and pseudo-desktop monitors in the market even with current windows XP and Windows 7 which are no way touch-friendly.
Let,s wait and see. I don,t think MS is going wrong here. Not at all I guess. It,s just my guess BTW.
BTW my another prediction: after MS will launch this, you will see atleast few linux distros following a somewhat similar approach. They have to do this to stay in competition. And we still have to see what Apple comes out with, in reply to this. Very interesting indeed.