I must confess I don't really know either way, but he makes a good argument :) So if you have any further points I'd like to hear about them, although it might blote the list a bit.

Well, I would say the main argument, from my point of view, is that you get the power of xml. For instance, you can use MathML (http://www.w3.org/Math/) to enter mathematics in a pretty good way. Check out for instance the examples at http://www.w3.org/Math/testsuite/, with a good browser, e.g. Firefox. Being a mathematician, that's one thing for me in favor of XHTML. I'm sure other people can list other uses of XML. 

I have not messed around with Javascript, so I can't comment on that. 

Haris