mod_pagespeed seems to work fine
Im using
Centos 6 64 bit
Zend Optimizer+ OpCode cache
mod_pagespeed
and Varnish
among other stuff
Varnish was the trickiest so I documented it here
http://badlywired.com/technical-stuff/2013/09/27/setting-up-varnish-with-virtualmin-centos-in-5-steps/