It's a tablet, it's a netbook, it's the best of both!
When all you have is a hammer, every problem looks like a nail. Microsoft seems to be making the mistake that tablets are going to fully replace PCs. They aren't. They, like phones, are going to compliment them. Each is a different tool with different strengths and weaknesses.
There is a reason people don't use iPads and the like for serious spreadsheet and keyboard-based work. They aren't designed for it. Slapping a keyboard in the cover isn't going to change the fact. You can already get keyboards for the iPad and Android tablets.
Yes, they work in limited scenarios, but that doesn't mean people are going to give up full tactile respone and 27" monitors when doing long typing sessions. You think people have issues with carpal tunnel syndrome NOW, wait until they're doing all their typing on one of those things!
Most typical office tasks involving the classic Office suite of products aren't going to change. Those tasks still need to be done, and spreadsheets, word processors and heavy data entry aren't going to disappear anytime soon.
It is the software that drives the hardware. Microsoft knows it. Ballmer's famous "developers, developers, developers" chant is proof of it. Apple knows it, too. This is why they continuously tout the number of apps available for the iPad. And it is why, despite my dislike of Apple's walled-garden approach, I'm getting an iPad. There are apps there to support private pilots that just don't exist on Android (or Windows 8). LOTS more.
Microsoft pushed tablets for over a decade. They didn't sell. Microsoft's interface and applications don't work well in touch format. Windows Metro may change the OS interface, but I fail to see how data-entry heavy applications like Word and Excel are going to work any better than in the past.
Microsoft will sell a bunch of these, simply because they'll most likely dump a wad of cash into promoting them. But, unless they come up with more compelling reasoning that "you don't have to give up Office" for these, I can't see them passing Android or Apple on the sales charts.