What's the latency to GET an object from S3 from an EC2 Instance.
For example, how many ms before the actual data stream for that object starts streaming back when requesting a object by it's full path.
Latency, not Throughput.
I don't think AWS makes guarantees about latency, but using S3 from EC2 is definitely going to be faster than doing it over the web. If you want to get an idea of how well S3 performs in practice, check out http://www.cloudstatus.com/. Unfortunately, that site only gives throughput statistics, but I figure you may be interested in that anyway. You may also be interested in their availability guarantee: http://aws.amazon.com/s3-sla/