The main uses for XML, at least at my level of understanding, will be to warehouse data in XML files and to provide a standard for inter-application communications.
You still have all the problems that non-standard browsers create when you are presenting the information, because it will still be presented in html.
If you are interested in reading, there is a nice new article about setting up XML/XSLT to serve HTML, WML and PDF files from the same XML file at
www.devshed.com/Client_Side/XML/INTCXX/ You could also use this technology to create two seperate html files from your XML, one for IE and one for Netscape.