We have PHP 5.0.4 on our new servers and MySQL 5.0.24-standard. We've setup our new servers with new versions at the time of loading cpanel on the servers and thats the best way to keep customers happy on a new server as those who see any coding error with php 5 will modify their code rather than complaining.
Upgrading php and MySQL Server version on old servers is not easy as there are many customers who get upset with the errors and they think that we messedup something on their
website hosting to bring those errors.
Customer service becomes easy when you have updated version of software on the server at the time of setup of server.