Great
Don't know if you've seen it already, but you may also want to consider ezUpsell, it removes x-carts forcing of them into the shopping cart before they are ready (or the option of staying on the same page which confuses them as to if the product's been added) by giving them the option of Continuing Shopping or Checking Out.
http://www.websitecm.com/store/customer/product.php?productid=84&cat=0&page=