For years I worked strictly with Drupal and assisted with development of core and modules. I've recently started using WP more and more. I really like Gravity Forms and the power that they have however there's one thing that I really miss from one of the most popular Drupal form addons called WebForm and that would be the ability to restrict access to the forms based off of IP's and cookies for select time periods.
Granted, I can achieve such results by modifying my functions.php for each form and adding some custom code. With many forms that can make for a very long and messy functions file, which I'd rather not have.
The reason for this method, over the email method that's currently in place, is because many times spammers (non-bot) will attempt to flood non-sense through repeat postings when you have a form with conditional recipients. Because gravity forms does no actual email check, other than verify the format is correct, the spammer can use any gibberish email they choose.
Another example would be for coupons. For example: When the Gravity Form is submitted it subscribes the submitter to a MC group that sends an autoresponder coupon within 24 hours. The coupon is offered as a thank you for them filling out a survey. They don't want the same person to fill out the survey every day, but should the client request another service a month later they would like feedback on that service as well.
Some people, like myself, have over 5-10-20 email addresses and limiting submission by just email address in this day-and-age is silly. I don't know anyone that just has 1 email.
Maybe you can keep this into consideration when adding future features. Since the IP address for every submission is already stored I don't think it would be too difficult.
