A conditional function would allow a person building a form to hide or display additional fields based upon a response from a user filling out the form.  For example a parking registration form could require a student to identify each vehicle that he may take to school.  The student could select 3 from a drop down list to indicate the number of vehicle he may park at the school.  The form would display 4 additional fields(make, year, color, license plate) for each for all 3 cars (12 additional fields total).

Logic functions would allow us to require those additional forms be completed in order to submit the form.

Addition payment functionality to custom forms would also be a bonus.