There are three major changes in this release:
1) Better multi-lingual support. Searches are now restricted to the language the user is viewing, and there are new language options in the setup screens. If you are running a multi-lingual site with the Internationalization module, you may need to install a fix. See this issue for details on the multilingual support:
#662282: Support for multilingual sites
2) Some users were having permissions problems with Search by Page Nodes. These were caused because during search indexing, the "cron" job was behaving as the "anonymous" user, so it was not able to index content that was only visible to other roles on the site. So, you can now choose a role to use when indexing your content (when searching, permissions are still maintained correctly, but this allows you to choose a role with more permissions so that those people can still see content they should see in a search). See this issue for details:
#605458: Search by Page does not return all results
3) Search "environments" feature. This allows you to set up multiple search "environments", each with its own settings, and search each environment on its own page, with its own block, independently. See this issue and the README.txt file in the distribution for details:
#492878: Multiple search types
There are also some other issues that were fixed for this release:
#706134: Theming support - added the ability to theme the search form