Morphon Technologies has made available Morphon XML-Editor 3.1 and Morphon CSS-Editor 1.3.6 available for free today.
Both are written in Java and run therefore on a wide range of systems.
I'm just downloading it but it's damn slow. Perhaps their server wasn't prepaired for the load after giving it away for free ;-)
I'll tell you more, when I was able to try it out!
I could now have a look at it and have to say, that it's really worth a try!
It uses an CSS-based WYSIWYG editor to edit your XML files.
I've tried it out with docbook and it really looks great!