I'd like to be able to see the total stock value instantly, for me to have a snapshot of how much cash is tied up in stock. The system could calculate the value of each stock line by multiplying the quantity in stock by the cost price. The value of each line could then be added together to create a total stock value. The total stock value could be displayed on the summary page or products page.
Filtering the products in the products page to see total value of groups/categories of products would also be useful.