This subject is likely to be of limited interest to most, but actually that's at odds with the reaction you get when asking people about the protection of their systems and data. Whatever your choice, you really should take an interest in the subject.
Why? Simply because it's the DNS service that translates your request into IP language. For example, you know you must type in "
www.mybank.com" rather than clicking a link, but you depend on your DNS service to turn that into an IP address that you hope (!) is not
www.bankrobbers.com (actually DNSSec may improve matters, but that is not necessarily in place or supported at client end). Whether this is a malicious attack or an ISP related substitution (eg your ISP search page for a "not found") it is un-asked for behaviour.
Then, your DNS provider is also tracking you (or at least, able to) by IP address - at this stage in the transaction the sites you are visiting are in clear, not encrypted.
Also, you may (?) get better service, DNS servers are potential targets for DoS attacks, ISP DNS rarely have capacity to manage. Large DNS farms may give better performance. Open DNS provides better protection against malware and BotNets, too.
All this brought about by Cisco's Open DNS (208.67.222.222 208.67.220.220) going down last night and me having to fail back to Google (8.8.8.8 and 8.8.4.4 so nice and easy to remember)