I use it on many of my sites for both CDN & some firewall security. I use the Pro plan for a handful of sites and the free plan for smaller sites with less traffic. I'm happy and have no intent of leaving them anytime soon.
Not a big fan. It was put on a big site i managed a few years ago to prevent Ddos attacks. A good cheap solution if you can't afford something more exclusive to your server or lack the resources. Overall though, nightmare. Would constantly block legit traffic, and you are at their mercy if they go down.