This is what I sent to Udit:
Ultimately, this is something you are going to need to test. There is no way for us to know how Gravity Forms will perform in your environment with your specific form and under your expected load. My recommendation is to review our refund policy (we have a 30 day refund policy) and then purchase a Gravity Forms license. Install Gravity Forms in your staging environment, and stress test the form with your particular theme and configuration and any other possible add-ons you may be using. Testing is going to be key here, and as you find hurdles, you can attack those one at a time. Thank you for considering Gravity Forms for your important project. Please let us know what you find out.