My Continuent colleagues Linas Virbalas and Alex Alexander will be giving a talk entitled Building Tungsten Clusters with PostgreSQL Hot Standby and Streaming Replication later this week at the PG-East Conference in Philadelphia. I saw the demo last week and it's quite impressive. You can flip the master and slaves for maintenance, open slaves for reads, failover automatically, etc. It's definitely worth attending if you are in Philly this week.
Looking beyond the conference, we plan to be ready to support Tungsten clusters on PostgreSQL 9 as soon as it goes production. Everything we have seen so far indicates that the new log streaming and hot standby features are going to be real hits. They not only help applications, but from a clustering perspective queryable slaves with minimal replication lag are also a lot easier to manage. Alex and Linas will have more to say about that during their presentation.
Meanwhile, I'm sorry to miss the PG-East conference but wish everyone who will be attending a great time. See you later this year at PG-West!