My example may be a bit convoluted, however it does strike me as a bug so I thought I'd report it.
I have a display node for a product, and then blocks that also show on the same page provided by Views / Context.
One of these blocks holds the add to cart form for the product which the display node references.
If I try and add to cart using the form in the View, no matter what Quantity I specify, only 1 is added to the cart.
If I remove the Add To Cart form from the display node (hide it in the content type) however, then the Views form works as expected.