The same goes with PostgreSQL. Replication isn't a one-size-fits-all need, and companies like Affilias will find Slony much easier to work with than the built in PostgreSQL replication because Slony allows for seemless, zero-downtime upgrades, partial replication, and a whole host of other features. On the other hand, Slony allows for partial replication.....

You also have Bucardo which can do master-master replication between two nodes, and a few other solutions out there.