There is a theory about humans and robutts, and humans and CGI, it's the idea that we recognize that they look human, but the differences still alienate us from seeing them as human and life like, realistic, there are subtitles to our behavior and appearance that are as of right now beyond are ability to successfully emulate. The eyes and general posture and fluid movement being the most difficult. This is a game coming out for PS3 called Heavy Rain that is doing the most to cross the gap of the valley of disbelief, it's simply fucking amazing, and you all need to check it out, watch the HD version so you can catch all the subtleties.
http://www.gametrailers.com/gamepage.php?fs=1&id=2717