"A great base for a great new direction in personal computing", whatever. That's nice in a research lab. What consumer and businesses need is an actually useful operating system here and now. Your constant old/new legacy/future 90s/today rambling is just vague arbitrary judgement calls void of substance and meaning. Throwing away a mature and incomparable ecosystem of consumer and professional applications does not magically create value for anyone. The emergence of new interaction paradigms, simply because they are new, does not obsolete older interactions paradigms that excel at other things (like productivity, precision, comfort, etc). Apple invented the iPhone yet did not try to turn their Macs into large iPhones with keyboards.
Different interaction paradigms for different needs. FYI, command-lines are still around because command-lines are still the best UI for certain tasks.
The more I read dotmatrix's posts, the more I think this -> some people liked MS so much and was so desperate for changes to occur, they can't wait to hop onto the W8 bandwagon before even using their head to what's going on. So far the argument of change must occur from the legacy desktop to 'modern' UI is the weakest stance so far.
Modern UI isn't "tacked on" to the desktop - the desktop is now an app within the Metro UI. And, yes, changes needed to occur. The old ways of doing things, are being pushed out for new ways. The old, desktop/file/folder based computing is loosing ground to new app based paradigms.We're also moving towards new input methods - touch and motion sensing the biggest two. And what precision are you talking of? The mouse offers no more precision than my finger does. I have a 1680 by 1050 screen, getting a ridiculously small 1x1 strike zone, to precisely hit a specific pixel is damn near impossible - and it only gets worse as screen resolutions get higher, and the pixel density gets deeper. That level of precision isn't needed by people, and those that do need it, use other more specific tools for the task.
You're not going to be having a good day trying to do all of this on the desktop. It was built in a different day for a different age, and it's starting to show. In this day and age, devices are key, not desktop PCs. They are just one device among many, that need to work and play together. This argument isn't void of meaning, just look around you and you'll see it.
Also, they haven't thrown away the desktop, like I said it's still there, within the Metro Start Screen. But all those features, you'll start to see deprecated, and transformed into the Metro UI, The Control Panel being the biggest evidence for that. Soon, the desktop will be replaced, and emulated for only the advanced users still wishing to run that one desktop app, while everyone else works, and plays in the Metro environment.