Well, from experience, all i can say is that putting an Xblack monitor like the one mentioned here and any other one side by side, the difference is really REALLY striking. Howeve i have not had the chance of testing one to see if there is loss of detail on dark and things like that. For example, my Samsung LCD HDTV has an option called "Dynamic Contrast" which creates the illusion of deeper blacks, but by doing so it loses a lot of detail in dark scenes - everything's totally black instead of being what it should be. So i just keep it off. It kinda gives a more striking look to the image, but personally i like to see people's hair, and not just a black thing on their head (that's how bad it is)... Things like that.
Not sure how the Sony handles this.