Here's a photo of my niece wearing her bag/hat. (My apologies for the poor quality--it's a camera phone pic.)
It seems the confusion as to whether it was a bag or a hat was started by her dad who thought the bags were hats. My sister, of course, knew they were bags but wasn't home when the box was opened.
Last night, my nephew used BOTH bags to Trick or Treat and managed to fill them both. My niece decided to use a punkin treat bag instead, which is fine. Whatever carries the most candy and works best for you.
Still no photo of my sister wearing a bag hat, though she did tell me it was really really warm when she wore it.