Review Board 1.5.4 is out the door, with some good bug fixes and new API functionality some people have been asking for.
We've extended the new API to bring back support for updating change numbers on review requests, and to update review requests based on change numbers. The next release of post-review will use this when working with Perforce.
There's also new API for creating, modifying, and removing repositories, which should help for large deployments tracking hundreds of Git repositories. The Repository API documentation go into some detail on this.
Along with that, we have several small fixes for problems reported since 1.5. Most only affect certain users.
Release notes are available with the complete list of fixes and improvements.