Have been using w3TC for long, never had a single problem. Most effective and COMPLETE caching plugin, by far :)
After a recent move to a new server, i noticed error log in public_html, full with lines like this one:
[21-Oct-2012 06:10:54 UTC] PHP Fatal error: Call to undefined function w3_url_format() in /home/radicio/public_html/wp-content/plugins/w3-total-cache/lib/W3/Plugin/PgCacheAdmin.php on line 213
All look like this one, only time stamps change.