I updated the MyBrowser sample XULRunner application. It now includes a nsIWebProgressListener implementation that updates various browser UI elements in the expected manner.
It seems that my last post was missing a pointer to a sample XUL application ;-) I went ahead and posted a simple example application here.
Get your XULRunner nightlies here.
[edit: looks like some of the mirrors haven't populated the latest-trunk directory yet]
There are more XULRunner tinderboxen online now. Thanks Chase!
We're very close now to having nightly builds up on ftp.mozilla.org :-)