very interesting. one of the reasons we picked mysql for a very high-volume app over postgres is that we have RDS and didn't want to do backups/snapshots/etc. Could we now use RedShift as a postgres-API RDS?
You wouldn't want to replace RDS (or MySQL/postgres) with Redshift for OLTP workloads. Redshift is built for analytics and complex query workloads. The major benefit is the ability to do MPP (Massive Parallel Processing) and distribute the work out to nodes. I believe you can have up to 100 nodes in the cluster with the 8XL machines and 32 with the single XL.
RedShift is tuned for analytics, so if you're using MySQL today for analytics, it could be a good fit. But if you're looking for more of an OLTP engine, RedShift is probably not the right choice for you.