The problem is the threat of tablets. Apple's solution was to scale up their phone OS, keeping the tablet form factor completely separate from the laptop and desktop. Microsoft could have done this with Windows Phone 7. Instead they are betting on a future where the "tablet" is merely another PC form factor, with the user plugging it into some sort of dock to transform it into a laptop or desktop form factor, complete with the expected ports and peripherals. In this future users would want to have the same interface and apps across both modes.

Microsoft's own Surface centres around this perceived future; while usable as a pure tablet it ships with a built-in stand and removable "touch cover" (keyboard and touchpad) so the Surface can also be set up like a laptop form factor. Many of the OEM offerings for both 8 and RT are taking the same approach. This is in stark contrast to Android and iOS, where tablets are rarely/never sold with such peripherals in the box.

Microsoft have already started running TV ads showing off Metro to lessen the inevitable confusion. The severity of the transition may actually make its reception more positive than the Ribbon; the Ribbon was an unfamiliar feature intruding into an otherwise unchanged environment whereas Metro is basically a clean sweep of everything but the brand name, with the familiar only seen if specifically requested. Many everyday users only want a PC to do social networking, email, internet, games and a bit of Word, which is why many have been quite happy with the similarly unrecognisable iPad, and Metro simplifies these tasks in a similar way.

If Microsoft can sell users on the concept of a single device that serves all uses then this risky move would put them in a very comfortable position, leaving Apple and Google struggling to catch up since their products are in no way a "real" computer like Windows 8 (and even Windows RT). iOS and Android are ultimately mobile operating systems (iOS doesn't even support mice), and many tablet users still keep a computer around to do all the things these can't; Windows 8 and RT are still Windows under the hood, making a secondary device unnecessary.

I'm a long way away from choosing something like the Surface over a traditional laptop, but I'll certainly be interested to see whether Microsoft's picture of the future becomes reality.

This is an area where Microsoft's own precautions could work against them; because of the sandboxing approach WinRT apps have to talk to hardware sensors indirectly through APIs, so if Microsoft hadn't implemented it themselves it couldn't exist at all in Metro apps, and that would be one less check box for OEMs to brag about (it would also inconvenience developers wanting to port their apps to/from Windows Phone 8, which also introduces NFC). Unfortunately this approach means that attackers could potentially target vulnerabilities of the sandbox itself rather than relying on the user happening to have a particular vulnerable app or vulnerable version of an app.
At least one NFC-enabled Windows 8 device will ship in October (the Lenovo ThinkPad Tablet 2), so I guess we'll soon find out whether the WinRT approach makes NFC more or less secure. Hopefully Windows only listens over NFC when NFC-capable apps are installed...