The Varnish-Joomla pack has been upgraded to support Joomla! 3.3 which has been released last week. Existing clients are eligible for a free upgrade after contacting us.
Originally we planned this release to support Varnish 4 which has been released two weeks ago, but it was more work than expected and clients were more interested in Joomla 3.3 support.
Varnish 4 doesn't bring any significant performance gains for small-to-middle sized web sites, it has separate backend and frontend processing threads, which could be better in certain high-traffic scenarios. It looks like this release was more focused on cleaning up the Varnish Configuration Language and bringing log analysis features (which are awesome, by the way).