IMO this is dangerously harmful advice. Even if you do the Full SSL (Strict) version, you are trusting CloudFlare with all data. It's probably fine if you are just doing a static site or something, but the fact that CloudFlare has access to users' passwords gives me the creeps.

(You are also trusting CloudFlare to generate the private key of your web server, which is no big deal if you are already using their services between you and the user, but might be more complicated if you decide to trust that cert for internal use.)

Ultimately I only recommend this if you want a fast fix to prevent public wifi operators from injecting stuff into your HTTP content. Any other use and you'll not be able to sleep at night wondering what kind of data CloudFlare has stored.