Hi Cory,

You're asking if XML is popular?  Yes, it is very widely used.

XML is a very popular format, and it is used all over the place.  A couple of examples:  the newest HTML standard (XHTML) is defined as a subset of XML, Web Services use the XML-based SOAP protocol, even Microsoft Word and Excel can save your documents in XML format.  A lot of websites offer XML-based Web Services as well - several of the popular Geocoding and Mapping API's for instance.

Some of the things that make XML popular are it's human-readable format, its ability to be easily created and read on just about any platform, and the capability of "transforming" an XML document into another XML document very easily.  One very common example is using XSLT to convert an XML document into an XHTML document for display purposes.