The Google product manager responded to TechCrunch saying "no blocking, hijacking, or filtering" and responded on privacy with "Collected data includes IP address (up to 48 hours, to detect malicious behavior against the service), ISP information and geographic information (2 weeks each). The data is not correlated with your Google account in any way."

http://www.techcrunch.com/2009/12/03/google-dns-opendns/