I just merged in a patch into 1.4.4+ and upcoming 1.5 that has significant performance improvements for Postgres. An upgrade to the latest 1.4.4+ is recommended.
The patch optimizes the way new records are inserted into tables, which in large tables could induce a lag between 20ms and 17s. On our production systems the lag was averaging 300ms, so it was quite significant. With this patch, it flies ;)