XMLmind is a strictly validating, near WYSIWYG editor for DocBook, DITA, MathML, XHTML, and XML. Because XMLmind is highly extensible, it may be also be used to create documents conforming to your own custom schema. Its users are generally technical writers who need to author large, complex, modular, documents. XMLmind is also available as attractively priced, "special editions" called: XMLmind DITA Editor, XMLmind DocBook Editor, XMLmind XHTML Editor. XMLmind Personal Edition is free to use by many persons and organizations.
Complete list of changes can be found here