I just switched to Google DNS. Before I switched I got a 38ms response time when I ping google.com, now I get 285ms? I'm in the UK. Is this why it's slow?
It's possible that you are suffering from mistaken redirection to a different CDN.
You should read up on how CDNs work (http://en.wikipedia.org/wiki/Content_delivery_network) but the gist is essentially that your DNS server determines which content node you're routed to. If your DNS server is your ISP's DNS server it's very likely that you're geographically close.
However, public DNS is usually anycasted to more general regions. In this case, you may be then routed to a content node which is close to the DNS node, but farther from you.
Google actually does support the EDNS extension in order to help solve this problem, but I find it unlikely that ping supports the extension.
This is a big problem with public DNS services. My research group will be releasing a project soon which seeks to alleviate the problem and dynamically choose DNS based on what provides you the best performance.
Edit: Actually I think I may be wrong about one point: IIRC the actual DNS clients don't need to support EDNS-client-subnet in order for it to be used. Only the DNS and authoritative DNS/CDN need to support it. Usually that's a problem because most of the major CDNs don't support it yet, but Google actually does support it on both their CDN and public DNS. Therefore you should be routed based on your prefix when talking to google.com, not the anycasted 8.8.8.8 node. Thus, I have no idea what's going wrong.
DNS has nothing to do with ping response times. A ping requests the IP address from the DNS server and then does the ping. On most systems the DNS is cached locally, so multiple requests will use the same information.
I don't think that DNS lookup time is included in ping's latency numbers. It probably does the lookup once per run, and then caches the IP. It wouldn't make sense to to the DNS lookup once per ping.
