One of my colleagues working in support recently had a customer ask them how they might disable customer notifications in WP eCommerce.  They were already receiving notifications from the payment gateway they had enabled, and they preferred those.  Luckily, it’s a simple one-liner to change disable customer notifications.

add_filter( 'wpsc_purchase_log_customer_notification_address', '__return_empty_string' );

Add that to a plugin or a theme’s functions.php file and you’re all set.  Worth noting, the __return_empty_string function only exists as of WordPress 3.7, so if you’re supporting older versions, you might need to take a different approach.