PHP security FAQ

Hi, i have a question concerning PHP and virtual hosting. Is it still true that we need Apache's suExec mechanism to protect the users against each other in a virtual domain setup? I think with open_basedir i can prevent users from (over)writing other users files. And with safe_mode on i can prevent evil things like system("cat /etc/passwd"); And when i set the directory permissions like rwx-----x dom1user /www/domain1.com rwx-----x dom2user /www/domain2.com (the directories in domain-tree (eg htdocs, cgi-bin) can have other permissions) i can prevent that the users read out foreign directories. So i can't see any reason why i shouldn't use the module version of PHP for a multiple domain setup. Or did i miss something? I would be really happy to hear your opinions. Thanks in advance, Chris