How fast is Facebook's HipHop?

Interesting enough, PHP is having a revitalizing patch. With PhalconPHP build using native C extension to house the engine of its framework but also HipHop, having gained the maturity and stability (all major PHP Frameworks including Drupal and Wordpress has passed PhpUnit tests when run on HipHop platform). But how fast is PHP vs OPTCaching vs HipPop?

Environment Execution Type time [300 req]

Regular PHP 19.873 sec
PHP + APC 6.396 sec
HipHop for PHP 3.896 sec