I don't know.
Currently, the Metro UI is very limited. Most of your desktop experience is going to be in Windows' native shell... meaning you'll be in a Win 7-like environment most of the time and jumping back and forth to the Metro UI.
I personally feel Microsoft needs to do some heavy thinking. If it weren't for my netbook, I'd probably not be using Windows that much. (macbook's are way too expensive for me at the moment)
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Windows 8 will have to be eye-catching and appealing. There has been a rapid increase in users who are migrating to a Mac.