We built an e-commerce shop for Scale Shark - a water conditioner manufacturer and retailer. This was built in Drupal 6 to take advantage of Ubercart for the online shop element of the site. We considered using Drupal 7 and the new Commerce module but it is still early days for that system and it didn't offer us the functionality that Ubercart offers us, right out of the box - particularly when it come to seamless integration with Google Checkout.