You don't even need to setup the client, if you have control over any number of intermediate routers, you can snag/reroute port 53 tcp/udp traffic any way you like. I tend to setup my home router to do this, so that all open dns traffic goes where I tell it to.

It's also advised to do so for unauthenticated users on shared/public wifi so that you can provide an agreement page/site. Also, so that unauthenticated users can't use DNS as a tunnel method, which is pretty damned cool, but insecure.