If you are interested in DNS performance comparison, I created a tool for comparing DNS query times of 16 different hosted DNS providers including Route 53, Dyn, DNS Made Easy, UltraDNS, Rackspace, SoftLayer, Easy DNS, Zerigo and a few others here: http://cloudharmony.com/dnstest
It is a browser/javascript based test that uses a wildcard DNS record and alternating between cached and non cached lookups to determine an approximate query time for each provider.