Free?!? How can this possibly be free?
W3 Total Cache provides every possible tool for optimizing WordPress site performance. If there's a way to get your site's pages delivered more quickly, it is probably in W3TC.
Yes, there are an incredible number of options, but complete site optimization is not for the faint of heart. The options are logically arranged and well presented. Just going with the defaults will almost certainly make your site faster.
The CDN option all by itself is a work of art. With just a few clicks, you can automatically have your large content items (images, etc.) delivered via your favorite CDN.
Finally, the support of the developers is superb. They are professional and responsive.