Just noticed that Jeff's JSON module (which is included as part of Dragonfly) encodes strings using the apostrophe (') instead of the double-quote ("). This is actually invalid JSON and will cause problems with frameworks that require valid JSON (like the latest version of jQuery, 1.4).
I've added this fix to the mercurial repo for Dragonfly, but just thought it was worth mentioning here just in case this trips anyone else up.