If you do it DIY then you can also use the same packaging for your on-premise deployment as well (i.e. no AWS). ECS etc are great but not everybody is running on AWS.
We should look at ECS though. Are you more likely to deploy if something is in ECS than if it's a straight AMI?
Though I must admit (1) I am not one of your customers, and (2) our BAA with Amazon prevents us from using ECS. We typically run node on ebs backed m3.medium instances running Amazon Linux.