On the Cognicast there was an excellent tangent (all of them were good) in episode 106, where Michael Nygard bemoans with the fellow Cognitect Craig that, despite all the hate from the JSON generation, the failed promise of XML was the ability (again, that is part, not the whole) to have separated data and presentation with schemas, so you would not have to redesign endpoints all the damn time.

http://blog.cognitect.com/cognicast/106

This is just one view, and I am sure I will be mercilessly downvoted, as this is a gross simplification of that point, but it was one of many gems in that episode. I might finally review XSLT as this once again affirms things other devs told me when they said do not write off XML, in the complexity of it is something interesting.