I just pinged Comcast, Google, OpenDNS, and Level 3's DNS servers...
Level 3 was the fastest
Followed by OpenDNS
Comcast and Google were about the same.
I think I'll put one dns from google, one from opendns, and one from level 3 (assuming level 3 is free).
In fact, I just did. Judging by when I type in a mistyped URL, OpenDNS's page shows up first, I'll assume it's beating out google, comcast, and level 3 is responding. I hate openDNS's search engine, but comcast's is worse. I'm tempted to just put google as my dns just to get their search engine on mistyped urls.