The latest version of Cart Viper 1.3.0 now allows you to optionally allow the customer to enter some additional notes about their order during the order process.
This allows for cases where the user wants to enter some shipping information or purchase order details during the order process.

As the store admin you can turn on the optional order notes using the settings page on the my account module.

Enabling the order notes textbox

During the order process the customer can then enter whatever notes they need, the notes will then be visible to the store admin when viewing the completed order.

Checkout process with the optional notes field displayed