It has the virtues of HTML without any of its limitations. XML is intelligent to any level of complexity. The information knows itself. No more unwanted thought. XML is a mother tongue for other languages, so markup languages like DickML and JaneML become possible.
Adaptation is infinite.
Custom markup can be created for any need. If markup describing how pepperoni pizza is different from sausage pizza is needed, it can be made. If markup describing the varying degrees of lumpiness in gravy is needed, it can be made. No more fixed markup to limit the categorizing instincts of the masses. XML is easy to maintain.