So far I'm impressed by what I've read about Amazon's Postgres instances. Maybe the reality will be disappointing, but (for example) the idea of setting up streaming replication with one click is pretty appealing.
Where did you hear this was an option? When we talked to AWS about their Postgres RDS offering, they were pretty clear that (currently) replication is hardware-based, the slave is not live, and you don't get access to the WALs that they use internally for PITR. Changing that is something they want to address, but isn't there today.
I was guessing from the description of their "High Availability" option ... but maybe it uses something like pg-pool, or as you say, maybe they do it at the hardware level.
"Multi-AZ Deployments– This deployment option for your production DB Instances enhances database availability while protecting your latest database updates against unplanned outages. When you create or modify your DB Instance to run as a Multi-AZ deployment, Amazon RDS will automatically provision and manage a “standby” replica in a different Availability Zone (independent infrastructure in a physically separate location). Database updates are made concurrently on the primary and standby resources to prevent replication lag. In the event of planned database maintenance, DB Instance failure, or an Availability Zone failure, Amazon RDS will automatically failover to the up-to-date standby so that database operations can resume quickly without administrative intervention. Prior to failover you cannot directly access the standby, and it cannot be used to serve read traffic."
Either way, if a cold standby is all you need, it's still a one-click option, lots simpler than setting it up yourself.