Please note that the DNS vulnerability does not directly affect DNS clients per se, but is in DNS *servers*, which the multitude of you are not running. If you are running a DNS server (named) on your Mac, you likely know that you are since it would take manual setup to get running.
This vulnerability in DNS servers *can* affect clients in that a server with a dirty DNS cache can pass the wrong data back to the requesting client... but this isn't the client's fault. It's the server's fault, which this patch addresses.
This distinction is important, and would otherwise probably be lost on the majority of the crowd here.
That said, you should probably install this eventually (and you eventually will via OSX update or this small one anyway) but don't get in a tizzy if you can't do it right this moment.