Don’t use Google Public DNS!
…well, thats just a catchy title, not completely irrelevant though. :-)
Nothing wrong in using Google Public DNS, but as noted by others, its not ideal for everyone — slowed down my speed about 250kbps, compared to my regular DNS.
So, here’s a great tool to search for fastest and nearest DNS available for your location — Namebench; Just install and run it with default settings and it will present you with a detailed benchmark of your current DNS and other available DNS servers that you can use.
OpenDNS works best (about 54% faster than Google DNS) for me right now, Sorry Google! :)