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The answers to this question will be extremely subjective, but I'll give it a shot.
First, there are a number of conditions to consider. What device are you using? What do you intend to use the device for? Windows 8 was designed primarily with a touch-screen in mind, hence the "Live Tile" interface. It's better-suited to use on tablets.
In my personal opinion, there are a number of unforgivable problems with Windows 8:
-It fails to commit to the Metro design language. That is, the clean, geometric, colorful look that informs the Live Tile interface. Windows 8 feels like two systems running at the same time. If I open a web browser in the Metro interface and then switch to the desktop, it's as if that browser window is gone.
-The Start Menu has been removed entirely, being replaced by the creative but unfortunately clunky Metro menus.
-It's noticeably slower than Windows 7 without offering a whole lot more functionality. It may be prettier, but the fact that it doesn't stick to one style is weird.
-All Microsoft apps have stopped using drop-down menus and have switched the the "ribbon" introduced in Office '07. It's a matter of personal preference but I hate it.
This is all personal opinion, but Windows 8 feels sort of like an extra set of "features" tacked onto a perfectly good system. It simply isn't necessary. Just my two cents.
And then there are those of us who firmly believe that XP was the last great OS, and that everything which has followed is nothing but glitzy bloatware. :-)