A lot of this stuff must be Radeon-specific because turning off the VGA port on my laptop with Intel graphics produces no measurable savings in current consumption. An alternative explanation is that xrandr --output VGA --off doesn't do what I think it does.
Similarly, changing my laptop's internal display from 50 to 40Hz does not measurably save power.
My laptop uses about 11-12W with the radios off, and the battery lasts about six hours, so believe me that if I thought I could save half a watt with either of these things, I would do it.
One thing that's not mentioned in the article, but might have been mentioned in the presentation, is tickless graphics. If my machine is just sitting around with a static image on the display, there's really no reason for the graphics chip to be doing anything at all. Is this coming some day to X.org?