I know this is an old discussion, but I think it's worth to add a probably better solution since I did not find any on the net. My scenario is that I want to move folders containing media files, movies, so copying takes a long time. Imagine moving a number of movies extracted from blu-ray disks and DVD's and you see what I mean.
Thing is that it is not possible to move a folder with content. But a file can be moved to another branch in the same folder tree as long as it is not moved outside the 'approved' folder tree. In my case it is approved by the user using the FolderPicker.
So, first I create a folder at the new location, then I rename the files to the path and name they will have in the folder at the new location, and finally remove the old folder.