Cloudflare is a great tool to add another layer of security to your Drupal website.
When setup correctly Cloudflare will act as a firewall to block malicious traffic to your Drupal website at the application level. Cloudflare blocks many types of attacks: cross-site scripting, cross-site forgery requests, and SQL injection attacks. User checks can also be enabled such as GEO IP location and browser integrity checking to limit questionable or unneeded traffic.
Cloudflare also acts as a CDN and has many caching and performance features.
With minimal setup time, it is a no brainer to setup Cloudflare. Simple setup for additional security with additional benefits of better website performance.