Been playing around a little at work with these. I was given a rather mundane task of presenting a list of constants, pulled out of the sourcecode for our current project on the fly for use by the developers. The php code to do so and generate the XML took about twenty minutes and then I set about investigating XSLT.
Using an XSLT Tutorial and the source code from Google Sitemaps Stylesheets, I knocked up a couple of Stylesheets, including one with sortable table columns. I couldn't get the alternate stylesheet thing to work with firefox though, don't know if I was doing anything wrong.
Would post some code but I might get in trouble.