Everyone hosting a website or service online is using a DNS service, We’ve used a few, 123-reg, GoDaddy, AWS Route53 and now Cloudflare. Cloudflare wins hands down due to the service the offer.
Yes, they are a DNS provider, and if thats all you want, then fine, but (and still free) if you allow them to cache for you, you get image caching, DDOS protection and various other great services. On top of that, if you want to use additional features, you can pay a small fee and get more. It’s simply a great platform, We’ve migrated all our customers DNS over.