Best websites for patent searches?

Does anyone have any insight into how legitimate these sites actually are? I'm curious about their business models, who owns them, or really anything else you might know about their reputation.

http://www.patentbuddy.com/#

http://www.patentauction.com/index.php

http://www.patentgenius.com/

http://www.patentfish.com/

http://www.patentbase.com/login.asp

http://askguru.net/index.php

http://www.freepatentsonline.com/

http://www.lens.org/lens/

http://www.boliven.com/

http://www.uspto.gov/

http://www.adm58.com

I'm looking for specific details regarding: http://marketbrief.com/

Wait, is there really nobody else who feels this way!?