This comment has led to some confused faces on the web. Doesn't the iPad demonstrate that you need a specific, designed-for-tablets interface in order to sell tablets? I mean, the iPad sells really well, so everybody should just copy Apple's strategy, right? Well, there are two things wrong with this line of thinking.
First of all, as I've already argued in my iPad 2 review, the iPad doesn't really have a tablet-specific interface. It's a classic desktop/WIMP interface, and a rather mediocre one at that. For what is clamored as a 'post-PC' device, the iPad is remarkably like a PC. Like I said in the review - enlarging buttons and using a finger does not a new paradigm make.
And here's the funny thing. Microsoft is the only one trying to at least take some baby steps away from the desktop/WIMP interface with their Metro UI. Especially on Windows Phone 7, Metro does away almost entirely with chrome, icons, and menus. Metro is a decidedly text-based interface (as far as looks go), where elements are not defined by lines or borders, but by text. Due to its sparse visuals, sharp contrasts, and utter reliance on text, Metro, for all its modernity, reminds me a lot of MS-DOS. At its core, WP7 is still a desktop/WIMP interface, but compared to the PalmOS/Windows Mobile/Android/webOS/iOS same-old same-old, Microsoft surely has the thickest veneer on top of it.
Second of all, just because the iPad is successful doesn't mean it's the only possible approach to developing a successful tablet. It's a logical fallacy to assume that just because a traiditional umbrella works well against the rain, there won't be another approach that might work equally well - or better.
Microsoft is trying to solve a problem the iPad suffers from. The iPad, for all its flashiness, is quite limited in its uses. It's somewhat adequate at consuming content, but it absolutely sucks at creating it. So, if you want to get actual work done (i.e., type more than three lines), you're going to need to bust out your laptop, or fire up your desktop. Sure, there are cases of people creating some truly remarkable things with the iPad (like Gorillaz using it to make an album), but heck, there are people who typed out the entire Harry Potter books using mobile phone numpads - that, however, doesn't mean the numpad is the new LaTeX.
If you want a glimpse into how Microsoft wants to fix this inherent limitation of the iPad, you need not look any further than the Windows 8 demonstration by Sinofsky and Larson-Green. Larson-Green demonstrated the regular Office 2010 running alongside the new Metro-inspired interface, which baffled Walt Mossberg. Why didn't the Office team create a Metro user interface for Office? Larson-Green's answer was telling.
"Well. [The Office team] may do something... In the future," she responded, "But, um, we don't think people should have to give up everything they know and love to get to a more mobile form factor. So people can plug in a mouse and keyboard, and use it just like they would otherwise."
Why can't I take my iPad 2, plug it into a dock with keyboard, mouse, and display, and then have it switch to a Mac OS X desktop? Why doesn't iWork on the iPad come with a full-featured desktop interface? There is nothing preventing Apple from doing this - the iPad 2 is more than powerful enough, there are no software barriers, and it would make a tablet infinitely more useful. No more laptop to lug around!
It would seem that this is exactly what Microsoft means when it says 'tablets are PCs'. Why limit a tablet to just consuming some simple media? Why not use the technologies we have today to make the device infinitely more useful by giving it the ability to act just like a regular, full-featured computer at the push of a button? Wake up, check Facebook on your tablet, go to work, plug it into a dock, and use it like a regular computer, with all the features and possibilities of a PC. Go home, plug it into a dock at home, and do some work from there. Go watch some TV, take the tablet with you, and enjoy it on the couch.
This is what Larson-Green meant when she said what she said about Office. Of course there's a team inside Microsoft working on a Metro interface for Office for basic viewing and editing of Word, Excel, and PowerPoint documents. Heck, it already exists on Windows Phone 7! Microsoft just wanted to show you could still run the full-featured Office on Windows 8 - because it's a core part of the value proposition I described above.
In theory, this creates a pretty compelling proposition from Microsoft - especially for businesses, since if Microsoft plays its cards right, these tablets+docks could be a lot cheaper than maintaining both laptops and desktops. I say 'in theory', because, obviously, this is a pretty lofty goal, and any number of things could go wrong.
When you look at tablets from this perspective, it makes perfect sense for Microsoft to work its way down from Windows NT, instead of working its way up from Windows CE. I'm not saying they'll be able to pull it off, but I do have to at least commend them for trying. They are trying to eradicate the boundaries between desktop, laptop, and tablet, and no matter how much I dislike Microsoft for their anti-competitive and patent troll behaviour, I like that idea.