We've just discovered after our first batch of subscriptions (n=65), that the declined people don't get any notification that their payment didn't go through.
The store owner doesn't get notified either.
He was surprised when he saw his bank statement and the numbers didn't add up correctly... the issue was easily found (the data at the bottom of the subscriptions page makes it very easy to figure out what went wrong), but we were thrown for a loop when we didn't get any email notification for the 5 subscribers (almost 10%) who got declined.
Is this something that is correctable, or on the list for a future version? Ideally it would be a custom email that would let us write a little note and insert "makeup payment" links as well as the 'update cc" link. But the store owner and the customer would both hopefully get it.