"David's fanboyness is just something I love"-- agree but I really love seeing this pic and then the one of them on the Tardis back when Matt took over, because the exact opposite is happening, and it's lovely :)
Honestly though. Can you imagine what River must have felt when he said those two emotionless words without the faintest glimmer of recognition as to who she was. She tells him later that he was doing a fine job of pretending to not know who she is, but I think that that was just a last desperate attempt to deny that her biggest fear was coming to pass. She knew that this was the very end for her...because it was the very beginning for him.