My comment: http://drupal.org/node/1244204#comment-6678836
provided step-by-step instructions for setting up and applying a patch (supplied by @bangpound - thanks) to get media_gallery-7.x-1.x-dev (as of 2012-Oct-30) WORKING SUCCESSFULLY with media 2.x.
I am now attempting to get the recently created media_gallery-7.x-2.x-dev working with media-2.x. However my first attempt has been unsuccessful, as described in: http://drupal.org/node/1865732
So what I want to know is: what significant differences are there between the current media_gallery-7x-2.x-dev and the working media_gallery-7.x-2.x-dev (as of 2012-Oct-30) with patch support_media_2.x-1244204-90.patch applied (from @bangpound here: http://drupal.org/node/1244204#comment-6669972 and using my steps to set it up here: http://drupal.org/node/1244204#comment-6678836 as already mentioned)
Sure, there are API differences - i.e. between the 1.x and 2.x versions but I'm interested in missing features that prevent media_gallery-7.x-2.x-dev from working.
What's different between mg 7.x-2.x-dev & media-2.x compatible *working* m.g. 7.x-*1.x*-dev (2012Oct30) + 1244204-90.patch?