I was just asking as the new WordPress W3TC plugin recommends the PHP agent for additional functionality.
I find that WordPress CMS is running my life. Whenever it asks for something additional, I go through a lot of work to find out how to make it work for SME. And its stuff that not generally important, just stuff like reducing my load page time by 2 secs. or raising my YSlow grade from a 90 to a 94. It's so important to me, but it's really not!