Choosing an XML editor can be a tedious process. As with most technical writing authoring tools, you need to find one that fits your specific documentation needs.
First, make a list of your requirements. Do you need a tool with user-friendly features and extensive help that will allow for an easy transition? Or are you looking for a slim and trim XML editor for some serious hand-coding? Perhaps you need a full-blown content management system, or a tool that supports a specific schema or DTD?
The good news is that you have plenty of options. Whether you're looking for a proprietary tool with an extended customer support plan, or an open-source editor that will help your budget, you should be able to find an XML editor that meets your needs.
Here is a rundown on some of the more popular XML editors.
Cost: $695 - $1395 depending on version
Strengths: Full DITA support, Documentum integration, collaborative editing, user-friendly WYSIWYG interface, extensive language support, simple publishing to various output formats.
Strengths: WYSIWYG editor, DocBook and DITA support, Eclipse IDE support (for Java users), support for multiple XSLT processors, query support for XML and relational databases.
Strengths: Great bare-bones XML editor (no WYSIWYG), small download size, customizable library of snippets, works with most XSLT engines.
Cost: $499 - $999 depending on version
Strengths: Graphical schema designer, database integration, plugins for Visual Studio .NET and Eclipse, support for Office Open XML documents, editor with multiple viewing options.
Strengths: Office suite and XML editing in one package, extensive user community, familiar word-processing environment. (Note that Open Office documents can be saved as XML, but does not handle translation or other tasks. You'll need to either create your own translation process or invest in one of the other more robust editors mentioned here.)
Cost: Call Sales (likely differs quite a bit depending on whether you want the full-blown CMS)
Strengths: CMS integration, content reuse, translation, dynamic content, familiar word processing interface, support for DITA and other standards, highly configurable.
A free trial version is available for most of these. Download those that you think might meet your requirements and give them a test drive. With DITA and single-sourcing on the horizon, an XML editor may quickly become one of your primary technical writing authoring tools.