I am using PHP 5.4.9, WordPress 3.5, and W3TC 0.9.2.5. I just started getting the following PHP warning in my error log. I don't know why it hasn't started until now. Maybe it has something to do with the latest version of W3TC.
[05-Jan-2013 23:50:00 UTC] PHP Warning: stristr(): Empty delimiter in .../wp-content/plugins/w3-total-cache/lib/W3/PgCache.php on line 824
I didn't take the time to see exactly what's going on there. But basically you need to make sure that the delimiter being passed to stristr() isn't an empty string.
Its no big deal, but it would be nice to see this tweaked in future. Thank you so much for the great plugin!