The 'required' attribute works in most browsers but isn't being used in GF for some reason.
http://www.w3schools.com/html/html5_form_attributes.asp
Specifically, in GF Settings I have the Output HTML5 checkbox checked, and the checkbox for my individual fields are checked as being required in my form. But the word 'required' is not be added to input elements as I would expect.
It would remove a couple issues I'm having with GF validation using both AJAX and page refreshes.