Excelons $399 Stylus Studio XML editor is growing into a decent competitor to the king of the hill, Altovas XML Spy. I found XML Spy still a notably better XML and schema file editor, but Stylus Studio has stronger XSLT (Extensible Stylesheet Language Transformation) features.
Stylus Studio 4.0, which shipped in June, gains an editable graphical tree view for schema and XML files (see screen, right), as well as the ability to debug XSLT style sheets.
The software has schema and DTD (Document Type Definition) support and can convert between the two.
Stylus Studio has an auto-completion feature for schema tags and attributes and permits auto-completion of normal XML tags if the file has an associated schema or DTD—a real keystroke saver.
The software also has a drag-and-drop mapping tool that generates XSLT code to convert one XML file format to another, a built-in XPath query tool and tools to generate schema or DTD files from XML code.