In thinking about this a bit more I do like what Rebecca said above.  Allow me to select the fields I want to keep and then allow a merge to occur.  I believe this would allow the current UI to be used such that the user info on the right is the primary user.  If selected items are then merged, then the other user's info can be deleted.

This would be a fantastic enhancement if I can drag and drop fields that belong to the user in question. Often times there is correct info in both users but merging doesn't always accomplish the task.  If I had the option to drag info and then delete info that is not accurate would be wonderful.