Here's some insight into why Metro is the way it is and why it's the default UI for Win8: http://www.reddit.com/r/techno...
Metro exists, specifically, for the segment of the population that (mostly) single tasks and doesn't want to get bogged down in the nitty gritty of the OS. They don't want multiple desktops or have 10+ windows open; they want to, in the words of pwnies, do nothing more intensive than watch cat videos. It appears to be a deliberate move by MS that most of the included apps suck for "power users" (Mail and Calendar get singled out) and that Office 365 is meant to run in Classic. And, apparently, it's why Metro is Win8's default UI; so-called power users can figure out how to nuke Metro and work more or less solely in classic desktop. Casual users would, apparently, never find Metro if the default UI were classic -- or, at least, they'd never use it since it's unfamiliar. And familiarity's a big deal when it comes to UI design. Think about it for a moment; it's apparently straight-forward make an app that returns the classic UI -- MS must have made it very, very easy to do so from the OS-side of things.
That's why, in large, part MS has been flouting colours! and customization! and Bing integration! in its marketing -- they're trying very, very hard to get media consumers to use Metro and like it.
But there are some very large problems to this. Metro is designed around touch and keyboard shortcuts -- not mouse. If you're using a touch screen, Metro's not bad once you grok that swiping from the edges of the screen makes stuff happen. But, damn, good luck figuring out hot corners with a mouse (switching between open apps is not, in particular, very intuitive). Or alt-tabbing. Or "type to find program" (in Win7 / classic, Windows key then type). But
The funny thing is that, by so forcefully going after casual users MS has incurred the wrath of people who need their PCs for work. And those people? If they have to set up a new PC for granny, the first thing they do is install something like Start8. For whatever reason, MS's marketing people have focused on the improved casual user experience for Metro and made it seem like classic is being phased out (apparently, it isn't). And
MS has become a deeply weird and schizo company. They're supporting a handful of separate UIs (Office: ribbons; Win8: classic; Metro). It's been marketing its new OS as being a superior choice for media consumers who have either already switched to smart phones and tablets or, simply, don't want to change from something that works well enough. The only possible way Metro on a desktop makes any sense is if MS is using it as a Trojan horse to get people to consider using Windows phones and tablets. But, damn. That's kinda' crazy.