We plan to completely redesign the shopping list when we develop the smartphone interface. I can't give you a date on that as we have a couple of more pressing development features we are working on but it is high on our priority list.
One of the features we plan to add is that you can edit the list - adding and deleting ingredients, adding quantities. We also would like members to be able to set up their own store-cupboard so you don't see ingredients on the shopping list that you know you always have.