Adopting XML: Tomorrow's Web

Editors [4]: And for the rest of you...

Serif Software have a set of extensions for Quark Express to do 'WYSIWYG' editing of XML. Ordinary users could use this (with a little training) and it is available now.
Excosoft Documentor is... odd. It's a quirky outliner which handles SGML and XML, and works (but you have to get used to how). Very nearly quite good: ordinary users could use this (with a little training) and it is available now.
XMetaL may be the holy grail: a near WYSIWYG editor which parses your DTD and lays out your document according to your CSS1 stylesheet, but also allows you to see tree views or tag views if that's what you prefer. [MS-Windows only]