Good day Frederick,
I'm on WP 3.8.1 and the current version of the plugin. (My site also uses Google PSS for CDN, which performs well. We truly love it and have it fully configured.)
We've been having issues with W3TC which I'll summarize.
I'm on a dedicated server with a busy site, subject to large traffic spikes at times. We had installed and were using APC, but experiencing 500's.
To troubleshoot, we consdered each variable at a time. We went through all other plugins and disabled them for testing, we went through the entire theme and made any necessary code block changes (there wasn't much to be done,) we ran myqultuner and made suggested changes to the d/b as well as with Apache, config, .htacces--- and of the like. This is includes a server side cron job (not c-panel. It reduces overhead.)
With only Google PSS on, we have zero issues. When we turn W3TC back on, we get 500's thrown during times of high traffic. Oddly, no 500's are showing in the error logs, and the server doesn't show heavy stress (as well it shouldn't given our work on optimization.) During the high traffic, if I turn W3TC off, the 500's almost immediately disappear.
It's difficult to wrap my head around what's occurring, other than to say we have an issue somehow connected to W3TC.
I've delved through support and the codex and cannot pinpoint any specific concern or resolution such as this, and wanted to pass this back to you for your thoughts given your experience.
I'm actually not opposed to the idea of hiring W3TC for professional plugin in config for the site and the server, but we cannot discern with a general understanding where the concern is.
Please let me know if I should provide more info. Thank you :)