Since we started using the CloudFlare (free plan) on a few sites a few months ago, it's greatly reduced comment spam and contact form spam. According to our CloudFlare dashboard, it's also blocked many botnet zombies and other threats, reducing the risk of sites being hacked. It also serves as a CDN (content delivery network), but sites were fast enough before, so there wasn't a noticeable speed improvement.
Here's how we set up CloudFlare for a WordPress site. The steps you need to follow may differ.
The Dashboard in your CloudFlare account displays analytics and threats.
Because the CloudFlare CDN provides caching, you may notice that some changes (such as CSS changes) don't immediately take effect. You can put CloudFlare in Development Mode to temporarily disable caching (for up to 3 hours). In the WordPress plugin (Plugins > CloudFlare), set Development Mode to On. Alternatively, log into CloudFlare and on the Websites page, use the Development Mode button there, or use the Pause CloudFlare button to deactivate CloudFlare indefinitely.
Many hosts allow you to enable CloudFlare from within cPanel. We tried this, but found that it only works if your domain begins with "www". To leave "www" off and use your root domain (like http://optimwise.com), you need to go directly to CloudFlare rather than going through the host. References: Media Temple, CloudFlare blog (comments), DreamHost blog (comments).
If your site uses SSL, you won't be able to use the free plan. You'll need to upgrade to one of the paid plans.
Have you used CloudFlare? What are your thoughts? Do you need help adding CloudFlare to your WordPress site? Contact us!