siehe PostgreSQL 9.0 Beta 3 Now Available:

The third beta release for PostgreSQL version 9.0 is now available. This beta contains numerous fixes and several changes since Beta2, including a final clean-up of Streaming Replication and Hot Standby. Please download, install, and test it so that we can move towards final release of 9.0.

Some significant changes have been introduced in beta3 which will require some applications to be re-tested with 9.0. These include:

* Fixes for hot standby:
o close walwriter filehandles faster
o fsync on master before sending WAL
o improved handling of archive cleanup (archive_cleanup_command and pg_archivecleanup contrib module)
o better handling of WAL record corruption
o change of standby delay settings and timing
* Fix for array handling in plpython
* Many dblink fixes
* TCP keepalive support in libpq
* Fix for checkSeek() behavior on old platforms (was causing pg_dump to occasionally fail)

Weblinks:
PostgreSQL
PostgreSQL Wiki
Using PostgreSQL on Debian and Ubuntu