All in all? I don’t like it. Looks like a template taken from Soulless MoneyGrab Inc. but with some added steam elements.
Change and innovation is not bad, but while perhaps not especially beautifully, the current user interface is pretty decent in the storm that is nowadays “looks over function”-mentality.
Edit: but as others have said, it would be nice if there was some kind of theme selector so people can make their own choices, or just fine tune Big Picture mode as it already follows a more simplified and stylished theme.