I don't get it? I was excited about XUL back in 2007 (call me silly) and there was a whole resource site dedicated to it, complete with documentation and examples. XUL Plannet (https://web.archive.org/web/20070607174323/http://www.xulpla...) if I recall it correctly.

Back then, I wrote a pretty slick client for some RESTful API (I think it was a photo browser for flickr).