This is great and all, but what does it really mean? I mean if my computer uses 100W less power, what is the long term impact? How may kilowats per year will that save me? What is the drawback?

I just read some of the article and while it sounds good, I'm not so sure it is going to be good, at least not for the highest end of the GPU spectrum. If the integeated GPU uses system memory for the frame buffer and you have say, 2 8800GTX cards in SLI, that would require 1.5gb (768mb x 2) of system ram just to move the data from the card to the mobo so it can be displayed.