If you made the decision to move your WordPress install from shared hosting to a shiny new VPS you should consider optimizing Apache by making some tweaks to your httpd.conf file. Apache is a fast, reliable, and flexible server but is heavy on resources by default. If you are running a small VPS, and using it just for WordPress, you can make some small tweaks to your configuration and get some significant performance gains.
# http://thethemefoundry.com/blog/optimize-apache-wordpress/