Take a look at this thread (http://moodle.org/mod/forum/discuss.php?d=56900) where a possible alternative to APC (Xcache) is discussed. Maybe one more for you to test.
When testing APC, a hint is to always set apc.stat=0 in your php.ini file - otherwise you'll get one or two blank pages .
Thanks, I will test these on my development systems. For testing, I am using VMWARE and just making a new copy VMWARE instance for each configuration so that one doesnt effect the other. I have seen some people recomend other PHP accelerators, but I have allot of faith your your advice.