In other shopping carts, upon successful purchase through a payment processor, the user is presented with an immediate link to download their mp3's. this url can be obfuscated to hide the actual location of the mp3s so that user's cannot guess the location of other files. This would be especially important on a site such as mine where I'm going to have thousands of mp3's.

Hello,
 
This functionality already present in ViArt Shop.
 
You can add links into your confirmation e-mails by using the {links} tag from (Administration > Sales orders > Payment Systems > Final Checkout Page) as well as automatically active them by setting an appropriate order status to automatic activation (Administration > Sales order > Orders Statuses > Your Status > Download Activation. This tag contains all links related to the order.
 
All links ecrypted so user never knows where the file is actually located like download.php?download_id=123&vc=123456789abcde
 
Thanks,
ViArt Support Team