One thing that concerns me greatly is debugging network problems. Up until now, you could use dig, nslookup and other tools to see how your computers resolves

One thing that concerns me greatly is debugging network problems. Up until now, you could use dig, nslookup and other tools to see how your computers resolves to help you figure stuff out. Now what do you do? also what happens when firefox uses this cloudflare, some other X application will start using Z, and the third Y. Also I work, and used to work for many small shops (under 50 people) in different industries. Its standard practice to have internal domains, sometimes even having different things on the same domain (ie mail.comany.co is diffrenet server form inside and outside the network). If you don't have AD (increasingly common here with apple and linux laptops being the 95% of users), you will have to go to each user on every device that has firefox and help him fix the settings. I would say just block it at firewall level, but it's not trivial, without breaking sites that use cloudflare.