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KDE 4 is very broken today (is pre-alpha the official definition?). GNOME will most likely never be in that state again.
So you're saying the system architecture of Gnome 2.x is the ultimate possible, and will never need to change? Sorry, but if you want to make something better in a fundamental way, you have to break it first. Either that or create a lot of compatibility layers to keep the old API, and only Microsoft has the resources to do that.