I maintain a lot of legacy PHP code on some CentOS 4 servers, and CentOS 4 comes with PHP4 (I only recently became aware of the PHP5 packages in the centosplus repository). I've long resisted trying to move to PHP5 due to (probably overblown) fears of broken code.
PHP recently announced the PHP4 end of life at the end of 2007 (with some security updates through 8 August 2008). So it looks like I've just about run out of excuses.
Makes me wonder what Red Hat will do about their RHEL3 and RHEL4 distributions.