I just stumbled over Jonny Wray's "Bio Browser" - a Swing based browser for the cancer bioinformatics web service from the National Cancer Institute that uses the SwiXml library that lets you build Swing UIs using XML.

You can try the "Bio Browser" using Web Start or get the source @ http://www.jonnywray.com/java

Now if you know of any other public Java apps using SwiXml, please let me know and post a comment here. I will write up a XUL News Wire story once I've got about half a dozen. Thanks for your help.