Manual window management is awful. Windows 8 ditched windows in favor of fullscreen apps. Traditional desktop window paradigms are powerful but obsolete.
Windows 9 unifies previous contrasting paradigms, taking design cues from all platforms and recent innovations.
Just an unofficial design concept, but damn, this is sexy. This is exactly what Windows needs - a combination of the old and new, leading to something seemingly far more usable than the monstrosity that is Metro in Windows 8.