I have created a CMS that supported different building blocks (plugins), each would output its data in XML and supply its XSLT for processing. The CMS called each block, applied the concatenated XSLT and output HTML.
It was novel at the time and really nice and handy to use.
all in VBScript, god help me
It felt like a great idea at the time, but it was incredibly slow to generate all the HTML pages that way.
Looking back I always assumed it was partly because computers back then were too weak, although reading other comments in this thread it seems like even today people are having performance problems with XSLT.