I don't like Cloudflare because of their advertisement method, If it is related to forum and blog then it can be bad for visitor specially If always ask for recaptcha verification.
I don't have a good experience with them. Slow speed in some country and many people block their IPs.
If you pay for their enterprise services, it tends to work rather well, as there are now multitude of ways to prevent an attack, outside of straight traffic overloading. One of the recent things that I have seen them add to their services, is the ability to route your emails through them, so that if an email server is attacked, it will not cause issues with emails getting to where they need to go.