I hate Cloudflare, to be quite honest. It messed up my sites DNS so much and their support was no help whatsoever. It also slowed down my site a bunch, they did more damage than they did good, so I won't be going back to them anytime soon. 😛
I've previously used their Pro service for about 6 months, which I found slowed down my site and considerably hurt our up-time, because their network was always having trouble. It seemed like the service was doing the exact opposite of a lot of the things it advertised.
My only encounter with them is when I visit a forum with it. Usually it give me a brief loading period which lasts like 5-6 seconds. I don't really have experience with it to really have a true opinion about it. What does it do exactly?