Drupal and PHP5 - GoPHP5
Follow @ggarronPHP5 has been around for three years already but it has not completely adopted by all webhosts which is a difficult for Drupal to use all PHP5 features in the development of this great CMS.
This should be also a problem for other PHP projects such as Wordpress, , and others, this is why there is a new movement called GoPHP5 and now Drupal is part of it.