If you're looking for a simple and easy XML editor, then XML Writer
has everything you'll need. I recently downloaded a trial version of this piece of software and was impressed.
Why an XML Editor?
The main reason I use an XML or HTML editor is for the color coding of text. It makes it much easier to remain organized when tags, attributes, comments, etc. are colored differently from plain text.
Color & File Types:
XML Writer allows you to set the colors for almost every different type of text, but personally I think the default settings are just fine. Although the program will open any file, it recognizes a host of different file types including: xml, xslt, css, html, xsd, and dtd. Each file type has a similar if not identical color scheme.
DTD & Schema: If you're working on an XML file and a DTD/Schema document is assigned to it then XML Writer can check to see whether your XML document is valid according to the DTD/Schema. At the very least it will let you know whether the document is well-formed XML which is always important to know.
The Bad (XML Writer's Paperclip Helper):
The only annoying thing is the automatic helper. When you're writing HTML, the program will automatically try to insert ending tags. It is annoying because usually I write the opening tag, then the text, followed by a closing tag. XML Writer tries to 'help' by entering the closing tag automatically which messes up my whole flow. This was the only thing that bothered me and I turned it off within 5 minutes of using the program.
If you work a lot with HTML or XML documents and don't like using over bloated programs to get the job done then this editor provides some great functionality with a clean and easy to use approach. Give it a try: XML Writer
You can download a trial version to test it out. The cost for single license is $99 USD.