Today, pg_migrator 8.4 final is released. The code has gone through many betas and has been completely overhauled since its last major release in 2007. It supports migration from Postgres 8.3 to 8.4 without a data dump/reload.
pg_migrator is designed specifically for experienced users who have large databases, where a data dump/restore burdensome. You can download pg_migrator, including a pre-compiled Windows binary, here: http://pgfoundry.org/frs/?group_id=1000235