Hey guys, had to chime in on this. We just installed Edit Flow and were surprised to see that in Calendar view we can't move posts around that are scheduled.
Let's take a step back for a moment, and consider this from the perspective of a site that has content scheduled out for say 30 days as we do.
You would look at the Calendar view, and looking at all the scheduled posts, you realize that certain posts make more sense to be re-arranged, i.e. too many posts on the same topic in the same week. or perhaps too many from one author in the same week, so you want to even them out - rearrange the publish date of a few posts.
So you want to drag and move them.
However from this same perspective of a site that publishes content, I really don't how dragging content that is not scheduled would be useful? :-)
the plugin "Editorial Calendar" handles this nicely - although since we're now using Edit Flow
Take a look if you're not familiar with it, the way they implement easy calendar dragging of scheduled posts is exactly in line with how a content publishing site works. :-)
Please let me know if you'd like me to elaborate a bit on the inner workings of this process flow, happy to help.