The plugin is fantastic, and in conjunction with hyperdb and db cache reloaded and memcache, my website loads instantly even though there are a large number of queries and assets to get.
However, i believe there is an issue with logged in users. I can accept that its not a good idea to serve cached pages as content will be specific to the user or user-level. So if i switch off caching for known users, then why does it take 5 seconds to render each page? It is as if it is generating a cache file anyway but not serving it.
Here's what i've found with the help of a server daemon "new relic" which is brilliant btw.
Switching caching off completely it takes about 1 second for an average response time for the homepage for logged and non logged in users.
Switching caching on with mod_rewrite mode, when there is a cached home page there to serve, it only takes 300ms to respond. Brilliant! The catch is though, it's only for non logged in users. If i am logged in, it takes 4.5 seconds to respond.
Why when I have tried known users on or off does it still take up to 5 seconds to respond, when if i disable the plugin it takes 1 second.
There has to be something we can do about this. It's not mysql, and it's not browser caching and its not external content causing a delay. It is definitely related to generating a cache file regardless of being told not to.
I am happy to pay for someone to come up with a solution!