Well, XML != XHTML and you very often use XML as an intermediate markup language when facilitating communication between webservices and applications and perhaps even AJAX. It's also great for storing data in an open-source manner. WebServices often communicate using XML. Automatic programming documentation, such as that from Visual Studio also uses XML to markup the comments and descriptions.

RSS = XML also. So all the feeds are made up of XML.

OpenDocument uses XML to store its data. DC++ uses it to store the downloading-list and the list of shared files.

XML and XPath/XSL can be used to yield great results when working with dynamic data, using XPath to select and XSL to style the data. CSS and XML also works great together and all XML can be styled by CSS using the CSS selectors.

XHTML is HTML with an XML markup which is great from a standards-viewpoint and also great if working with a CSS based layout - because if you then feel like changing a tiny thing you can easily do that with the same markup but different CSS.

So there are many good parts about XML.

Henke