It turns out that besides drag and drop reordering, the ordering itself needed a lot of work,
You can test experimental build RC9b 1590:
SVN Downloads
Changelog (summary since RC9b 1576)
1. PHP 5.4+ compatibility
2. Rewrote item ordering code (model/view/controller), to support ordering groups per category, per state group, per language, and to be able to save and reorder multiple groups per save operation, this for both FLEXIcontent ordering property and for Joomla ordering property,
3. Drag and drop item records reordering
4. J2.5/J3.0 Compliant installer (component install but does not function in J3.0)
5. Fixed a bug in notifications emails regarding draft state from publishers, and added selection of states for emails of new or existing items from users that can publish
6. Added usage of ACL edit/publish/delete permissions in J1.5 with FLEXIaccess like it is already in J2.5