This is the first Drupal Commerce site I have had the opportunity to work with. The site was designed by Kinetic Media (Australia). I handled the theme and most of the Drupal implementation.
The displays for product category pages exposed some of the limiations in Drupal's taxonomy system. The top-level product category pages (accessed through the main horizontal navigation) required a different layout and method of selecting products to display from the sub-cateogry pages (accessed through the drop-down navigation menus). Top-level product pages contain a manally selected list of products (managed using Nodequeue), while sub-category pages contain all products in that category. Unfortunately, Drupal doesn't have a good way of providing different templates depending on the hierarchy of a taxonomy term. To solve this problem, we developed a custom plug-in for the Context module which provides a context condition based on taxonomy hierarchy.