i was having the same trouble and couldn't find any solution for this in the forum.
the docs say it's a TODO (but they don't mention a release version for this?)
see http://doc.silverstripe.com/doku.php?id=complextablefield#todo ('Ajax-Sorting')
sometimes it's a way to have the sortable objects in the sitetree, as drag'n'drop sorting is possible there, but that might not be applicable for your scenario
in case you're willing to code it by yourself there might be some hints in this thread:
but i didn't really get it there...
Thanks for the answer :D, actually the "sortable objects in the sitetree" has already become a solution strategy for me.
This way I get the Drag and Drop and the possibility to decide the ordering.
Also I can immidiatly see, where the pages are.
Only thing was, I had to make my own virtual page, but this wasn't that hard. So my SummaryPages can have many pages. And the pages can belong to many SummaryPages. Thus I also got my many-many relation, too.