Bob,

I think you maybe missing another interesting product - DITA Storm.
It is available at www.ditastorm.com and would belong to the group of browser-based editors.

Bob;

Thanks for the great comparison of available DITA XML editors.  In my case it confirms my own findings, but it would have saved a huge amount of time had it been available when I started searching for development tools.

I looked into your evaluation specifically to see if you might have answered a few other issues I've been evaluating:

1. More specific OS support information.  Windows means XP?  Solaris means 8, 9 or 10; SPARC or x86? Etcetera.  While a large percentage of folks looking into DITA will be running on Windows XP, there are many high tech companies such as mine who must support users on Mac OS X, Solaris, HP/UX, AIX, and Linux.  So finding a single editor for all platforms is a real challenge.  Even those editors you list as "Java" aren't necessarily cross-platform if the JRE version they require isn't availble for a given platform.  Of course, it isn't absolutely necessary for the same editor to be used across all platforms, since XML is platform agnostic.  But from a large enterprise support perspective, a uniform platform for all users would be the best.
2. How well does each editor support non-text content?  So many technical writers come from the FrameMaker paradigm where integrated graphic and equations editors are available at the click of a button.  They expect that sort of integration in the XML world, but so far I haven't found any DITA editors that even mention such issues; they assume you're creating graphcs and equations somewhere else and then simply HREF'ing those objects.
3. What about extending the editor, or developing integrations with a CMS?  You've covered the out-of-the-box CMS integration, but what about those instances where the ootb capabilities aren't sufficient, or don't match a company's chosen CMS?  Including a few notes about the availability of API documentation, the scripting language used to develop extensions / plug-ins, and what communication protocols are supported would be great.

Looking forward to the next edition!

Bob Beims