In the current PayPal Add-On in combination with the User Registration Add-On we have the option: "Update user when subscription is cancelled.". I think it would be very powerfull to add an option: "Update user when payment is fulfilled to [field select]".
The [field select] should not contain al the WordPress user roles, but the fields within in the Gravity Forms. That way we can link products / subscriptions directly to user roles. New users could be created with the default role "subscriber" and upgraded automatically to the selected product / subscription role (for exampled: "paid_subscriber") if the payment is fulfileld.
We have developed something similar in the iDEAL Add-On (Dutch payment method):
http://twitpic.com/6jrnwl
Is this a feature that can be added? If so, how long will it take to add this? We could also develope this function with some custom code in combination with the "gform_paypal_fulfillment" filter.
http://www.gravityhelp.com/forums/topic/using-gform-options-to-manipulate-register-user-addon