Oh, and they have 24/7 phone support, that at least, last time I had to call, was US-based. I don't truly trust anyone who doesn't have good phone support. Ticket systems are great and all for low priority requests, but it's too easy for a place with only a ticket system to handle you in a low priority way.
[1]The transfer process is straightforward and the price can't be beat, but their domain management features are still incredibly immature. You can't have name servers set that aren't Cloudflare's, every time you go to domain registration, it wants you to transfer ALL of your domains. And bulk management of domains on Cloudflare is nonexistent: You can't even find the expiration/renewal dates of your domains on Cloudflare without visiting the page for each one individually. It's actually easier to find the expiration dates for all your domains that are not on Cloudflare (on the Domain Registration page). I do like it but they have work to do.
I've been very happy with Cloudflare's registrar myself, even though they aren't always the cheapest[1]. Cloudflare just silently auto-renews all of my domains so I never have to think about when they're going to expire. And I don't mind the lack of nameservers since I can't think of a reason to use non-cloudflare nameservers for any of my domains.
[1] Namecheap offers .io for $32 (not a promo, standard price) whereas Cloudflare charges $45.
Also "just silently auto-renews" is not an okay behavior for me either. Even when I have auto-renew on, GoDaddy sends me email notices around renewal time for any of my domains. I like to manually renew them a bit early to ensure there's no problems with payment processing. Obviously I have like a year until any of my Cloudflare-held domains renew, but if I don't get email notices in advance, I will likely look at transferring them away. Proper notice of account/billing activity is a must for trustworthy service.
For one, my host auto-configures a lot of features on the DNS for my domains. Cloudflare imports it, obviously, when I transfer over, but if my host changes something, Cloudflare isn't going to get it, and I don't even have the option to change my name server provider even temporarily for troubleshooting purposes. That's a big flaw, and Cloudflare will need to fix it to keep me.
I don't have any .io domains, but my understanding is Cloudflare keeps literally nothing for any of their domains, so presumably Namecheap was able to cut a better deal with the registry.
There are better registrars and some offer reseller accounts which is necessary when you manage a lot of domains and not all your own.
I imagine this causes referring 3rd parties that read small print to align their product with GoDaddy than a competitor.