We don't use it for anything interactive or user-facing, it's too slow for that. It's for some large+cold data that is used in batch analysis jobs that need to query out a small subset of the data using relatively complicated indexed queries. We probably don't get more than a few thousand queries per day through the system which is no big deal and basically free, but migrating this cold data to S3 allowed me to save a few terabytes in our expensive SQL Server cluster which is a big deal.