There can be potential problems. My router was supplied by Verizon and is hardwired to go to it's DNS server, which puts up a fake web page with links if you type in something wrong rather than returning failure. OpenDNS does the same (how do you think they make their money?). Google DNS gives the correct "not found" response. So I have to override the DHCP provided DNS setting (192.168.1.1, the router) in every computer to use Google DNS. But if I do that then I don't get DNS service for the systems on the LAN. Eventually I plan to use a Mac Mini Server to be my DHCP and DNS server, then I can forward requests to Google DNS and all will be fine again.
In general, if you have a local server, you want to use that for DNS as it will cache the addresses and be faster responding than any external server.