You can pick up a nice, free XML editor, Liquid XML Studio 2008, from Liquid Technologies at http://www.liquid-technologies.com/Product_XmlStudio.aspx. All the important stuff is there:
- document text editor
- intellisence
- schema graphical view
- document validation
- XPath builder
- XML formatter
- syntax highlighting
The UI has a Visual Studio look and feel. Without a doubt, the best free XML editor I've come across!