The price is nice, but what makes it a must have for me is the ability to generate a cert with 100 domains on it and have it validated by hitting the server.

The "old" way required all customers/domain owners to either give us control of their domain or to answer an email every time we needed to get a new cert. Now we've automated moving around domains between certs and generate new ones as needed. Validation by email to 100 different people is like herding cats. Validation that happens in an automated way - priceless.