XSLT, part 1

The good

Widely implemented, thoroughly standardized There are plenty of implementations in a wide variety of environments, not to mention a conformance committee at OASIS watching over the whole thing.
Useful beyond its original context Built for formatting documents using XSL Formatting Objects, XSLT has proven a powerful tool for a wide variety of data and Web applications.
Makes XML accessible via Web browsers Need a quick conversion of your XML documents to HTML? XSLT is probably the easiest route, letting you build flexible templates which you can process in both static and dynamic environments.
No side effects It may seem strange that variable values can't change, but that leaves open the possibility of massively parallel XSLT processing.