Compatibility problems with PHP 5

Hi guys, Now that we're at a very advanced stage and the code freeze is coming up, I think it'd be a good idea to start running some PHP 4 applications on PHP 5 and see how easy things go. I'm sure we'll bump into some issues and many of them might be solvable (using the already existing compatibility mode for object cloning or by other means). If anyone here has time or has already tried running some popular PHP packages such as php-nuke, phpbb, phpmyadmin and so on, I'd love to hear about your experience and especially the problems. Thanks, Andi