I just did this and it gave a strange result. Now all of the pictures that I manually moved from the "Members Galleries" category into more appropriate categories reappeared in the "Members Galleries". All of the posts reappeared. It does say that there are 0 pictures in every category though.
Also, notice that since the move to vBgallery, I moved the category called "Mud and Water" under "Places you Have Gone". Now the category "Mud and Water" shows as a main category, as well as a subcategory to "Places you Have Gone" with all of the same pictures in each!