Update: We've released an add-on to the plugin called Magento Warp
While the plugin works OK with Magento with minimal tuning, there's still quite a lot that needs to be done to make Magento run fast. Because Magento is such a complex stack, we've developed an Magento Varnish server offering that focuses solely on Magento. And it does wonders! Read more about the managed Magento Varnish server.