I've did some experiments - and yes APC is a little bit faster (1-5ms per page rendering) when used as key-value store in comparision to memcached via unix socket. However I had always problems with cache fragmentation and a resulting slowdown. If you use Apache mod_fcgid the PHP processes are beeing shot down and started at random and APC is is not shared acress them. With nginx and PHP-FPM is is not so true anymore. I've had the impression memcached is more solid.
For static caching I use nginx with fastcgi_cache. This makes WP-Supercache obsolete. I bybass the cache for requests containing certain cookies, so that logged in users always receive fresh pages.
Another big Wordpress performance sink is locales. If you have a blog in a non-english language consider using a language-caching plugin. Wordpress uses a PHP gettext implementation that is quite slow. 20% speedup if you cache the generated locales.
But it's a shame to spend days or months on tuning Wordpress, what is essentially just a blog engine.
For static caching I use nginx with fastcgi_cache. This makes WP-Supercache obsolete. I bybass the cache for requests containing certain cookies, so that logged in users always receive fresh pages.
Another big Wordpress performance sink is locales. If you have a blog in a non-english language consider using a language-caching plugin. Wordpress uses a PHP gettext implementation that is quite slow. 20% speedup if you cache the generated locales.
But it's a shame to spend days or months on tuning Wordpress, what is essentially just a blog engine.