This app could be so great, but the UI needs a lot of help. You can only add photos to the default stack for some strange reason. So you select a group of photos, press "add to stack", they go to the default stack. Then you have to go to that stack, select the photos again, select "move", and then select the stack you want them in...and hope they actually move. The only way I can get photos in the stack I want is to constantly change my default stack.