Review Board is still in development, but is approaching an official release. We'll be releasing once Django provides a new official release.
For time being, we recommend you use Review Board SVN. We work to keep SVN stable and usable in production environments.
Review Board SVN can be checked out by typing the following on the command line:
$ svn checkout http://reviewboard.googlecode.com/svn/trunk/reviewboard
Documentation is available to help with the installation.