I love the quote attributed to Chris Maden: "XML is like violence: if it doesn't solve your problem, you aren't using enough of it."
I disagree about XML being the right tool for the job. It is a decent hierarchical data description format. It's not great at describing various hierarchical and non-hierarchical visualization aspects and runtime interactions.
Microsoft somewhat recognized this fact while designing XAML. That's why we have markup extension language. Caliburn similarly introduced an action syntax to improve the deficiencies of XML format for this purpose.