We have added thread pool, query cache, and a few other minor things to 2.x series. That makes Sphinx 2.3.1-beta, now available at http://sphinxsearch.com/downloads/beta/ - read on for a quick overview of what was added.
We're happy to announce the public release of Sphinx Tools-beta. Sphinx Tools provides users with a SAAS interface to streamline the administration and monitoring of Sphinx instances. Essentially it's a single interface designed to make it easier for you to understand how Sphinx is behaving and make insightful changes when/if necessary.