Following a suggestion by Kay Whatley, DITA News has begun to collect the current DITA version compatibility for all DITA-related tools.
DITA vendors have been contacted and a preliminary table reports which tools are DITA 1.0 compatible, which 1.1 (or both 1.0 and 1.1), etc.
The URL for the Version Compatibility Table is
http://www.ditanews.com/tools/compatibility/
See the Tools A-Z section of DITA News for links to the tool vendors
http://www.ditanews.com/tools/