Tim Cook, at the D10 conference two weeks ago:

The tablet and the PC are different. You can do things with the tablet if you’re not encumbered by the legacy of the PC—if you view it as different.

Products are about trade-offs. You have to make tough decisions, you have to choose. And the fact is, the more you look at a tablet as a PC, the more the baggage from the past affects the product.

Compare this with Microsoft’s “no compromises” approach:

We designed Windows 8 to take into account the desire to have a PC that works the way you do—whether you want a laptop with a permanent keyboard, a tablet with a keyboard you can attach (wired or wireless), or something in the middle. Touch works across all of these form factors, and you choose which input method to use when. This is what we mean when we say Windows 8 provides a no-compromise experience.

And:

You may choose to carry a tablet, or you may choose a laptop/convertible, but you do not need to carry around both along with your phone. You never think about a choice, or fret over your choice of what to carry. Things just work without compromise.

These are two radically different approaches. Microsoft doesn’t necessarily look at the tablet as a PC experience, but they’re trying to combine it with one. Microsoft’s goal is noble, but it’s risky.

A tablet experience is very different from a PC experience, and combining them comes with a high risk of introducing design patterns that doesn’t make sense for one or the other experience. E.g., the Metro mode and the classic Windows mode differs in how to launch apps, how to navigate between apps, and how to close apps. It forces users to create two completely different mental models of how the OS works.

Windows 8 hasn’t shipped yet, so we’ll have to see how it turns out. So far though, Microsoft hasn’t made a good enough job. Windows 8 is running a high risk of turning out like this:

An OS that in theory pleases everyone and does a lot of things, but that in practice does all of them poorly. It will not offer a great tablet experience, and it will not offer a great desktop experience. It will offer something in-between, a confusing mash-up filled with duplicate features and inconsistencies, that you never know what to expect of.