I like this. They are priced at 25% of sendgrid, which we use as we send a million emails a month or so. But sendgrid provides a dedicated IP address. Having a dedicated IP over a period of time helps with delivery as the IP 'reputation' increases based on your delivery rates.

A lot of EC2 Ips are blacklisted by ISPs because people just create instances and spam away using exim/sendmail. If amazon and keep its IPs clean and also manage the service well, this is going to be THE email sending service to use.