Because they are acid-free they are great for putting together a family photo album. And the 3-hole area is outside the 81/2"x 11" protected space so you get the maximum room for photos without punching holes in them.
I'm not sure I'd call these heavy duty. But for my purposes they'll do fine. If I had anything that was thicker than regular printing paper such as card stock or a three-fold pamphlet I would have tried to find something thicker.