Mozilla 16 has a head start on MS I.E. regarding XML. Yet as long as you have a good .xsl file (stylesheet) with an HTML template that can have a CSS embeded (or not) you’re all set. You can view XML sites with MS I.E 4.0.
There really isn’t much out there but I found this as a good starting point What is XML? I’ve already download the XML notepad. It’s pretty damn good though it is beta 1.5. Works just fine for producing well-formed XHTML as well.
The project cool Behaviors for IE5 is interesting. The publishing goodies are very nice. The Footnotes effect will make long boring technical documents a little easier.