By the way, I wasn't really pleased with A.I., and I have zero interest in ever watching that again.
Only recently have I really "gotten" the last act of A.I., and hence explains the entire picture. And it really made me appreciate it a lot more.
Most people complained that the last act was tacked on by Spielberg in order to transform a sad story into a happy ending. But it really isn't a happy ending at all when you think about it. The whole movie really is a tragedy, not a fairy-tale. It's deeper than people realize.