In my experience RDS has been amazing, and I am a MySQL guy. I say it like that because as a MySQL guy I would much prefer to setup my own server and use a third party engine like Percona or Maria, but RDS(MySQL) performance has been incredible.

The only thing I would complain about is the lack of a proxy or load balancer in front of their Multi-AZ setup. With any failover you are forced to have a downtime of 3-5 minutes while DNS propagates.