Been kicking the tires a bit here with Drupal Commerce so far pretty impressed with what I’m seeing. The kickstarter is a good way to get up and going http://drupal.org/project/commerce_kickstart. Looking at the line items functionality of Commerce and Randy Fay has some great video showing the power that you can get with these at the commerce guys website .
There are a lot of possibilities with these I would like to see what it would take to build a type of Kickstarter clone. There is a screen cast on the Drupal Dojo showing how to do this but it doesn’t look like it is using the Drupal Commerce functionality.