How to set up APC on Drupal 7 with httpd + fastcgi?
We finally managed to set this up properly. 

Apc works fine for multiple processes with apache/2 + php 5.3.x + php-fpm + fcgi in FPM/FastCGI mode.

PHP 5.3.x is configured with following options
--enable-force-cgi-redirect 
--enable-fastcgi 
--enable-fpm