Have anyone considered using pgpool-II for this?
http://pgpool.projects.postgresql.org/contrib_docs/simple_sr_setting/index.html
I just started working on setting up replication for PostGreSQL and it seems the tricky part is when the old master comes back. I just start reading about it but it seems pgpool can automated most of that. However I'm not sure if it does leverage replication features already present in PG 9.1.