I'd be interested in an extension like this too, to sell downloadable music tracks. Is there any news on if or when it'll be released? If it works I might even be prepared to pay for it!
We implemented such feature 2 years ago in one project. The solution was to expose order history to the user with download link if the order status is 'confirmed'. There was no payment gateway though. Checkout process generated a bid for user payment. After confirming the payment Operator changes the order status to 'confirmed' and sends notification email .
