The approach I am taking to EC2 instances is that I can kill it any time. So fire up instance, fetch latest code zip from S3 (not from Github), and deploy that code. Runs smoothly.

Keeps it very simple and effective, I can even ramp up the number of instances then reduce them to retire old instances.

EBS adds another point of failure (and probably the weakest link in the Amazon stack) and overcomplicates deployment.