Instead of hunting for a public DNS server to use, you can just run your own. djbdns, for instance, comes "out-of-the-box" with a working cache. This puts some marginal extra load on the DNS roots, and so it's probably not a great idea for Microsoft to build it in as the Windows 7 default, but it's perfectly fine for one-offs.
In some limited testing, I find Google to be faster than 4.2.2.2, both to be faster than OpenDNS (which you shouldn't use, because they suppress NXDOMAIN), a local cache to be competitive with OpenDNS, and all of these options to be faster than AT&T's DNS, which is simply appalling.
(I test with nsping, which is a goofy program I wrote in the mid-'90s to test the resolvers at an ISP I helped run).
but only for a static ip. If you use OpenDNS on your laptop, and go use coffee shop wifi, unless someone else has disabled NXDOMAIN from that IP, you will get their NXDOMAIN landing/redirect page instead.
Which limits its usefulness to desktop systems on a static IP.
In some limited testing, I find Google to be faster than 4.2.2.2, both to be faster than OpenDNS (which you shouldn't use, because they suppress NXDOMAIN), a local cache to be competitive with OpenDNS, and all of these options to be faster than AT&T's DNS, which is simply appalling.
(I test with nsping, which is a goofy program I wrote in the mid-'90s to test the resolvers at an ISP I helped run).