Simple single line integration with the HTML forms without writing any API for email validation on page
It takes a while to understand the value provided by the service. Could be made a lot better.
I have been using it for couple of my sites so far. It really helps to prevent the email spams and at the same time allows my users to correct their typo mistakes if they made one. I have a lot lesser records with invalid email addresses now. No more bounces when I send emails. Its the most affordable and accurate solution. The best part is that it does not require me to write code to integrate with the API, its a single line copy paste in HTML.