I have recently used the custom consulting service to create a shopping cart and I can't rate the service highly enough.
Ross and Greg did a great job of creating what eventually became a complicated system that included web orders, telephone orders, shipping to different countries with different postage costs, taxes etc, invoicing, outputting the invoice to PDF, the list goes on, everything I threw at them they handled.
Sales from the website covered the cost of development within two months.
Jeff