This has been a bit of a confusing issue for several other people as well. Google Checkout allows for a parameter called "digital item" this parameter tells Google that the item being sold is digital and that there is not need to collect shipping information for the item. The Nice Google Checkout plugin includes this parameter in order to support/integrate with the Google Checkout API.
The Nice Google Checkout plugin only handles the creation of the product listing and the transaction information that gets sent to Google. It will not transmit any download information to the buyer. Therefore, download information would need to be sent manually by the seller.
If this was not what you were expecting and are dissatisfied with your plugin purchase, please email me your PayPal transaction id for the purchase and I will issue you a refund.