It could be a very performant transparent caching layer when combined with the fdw extension[1]. You can push down the true analytics queries down to Redshift, but cache the resultsets, rollups, facts tables, etc, in materialized views. Then have the full power of modern Postgres available for exposing your data warehouse. The more predictable performance and auto-scaling storage makes it much better than the standard RDS for that setup.
https://aws.amazon.com/blogs/big-data/join-amazon-redshift-a...