Lower Power Requirements
AOpen's i975Xa-YDG comes with a simple, twin-phase voltage regulator. Don't be surprised by that, because this solution provides enough power for Core Duo processors.
A low power processor certainly contributes most to lower system thermal levels and greater energy efficiency. However, the lower power also impacts the rest of the platform: Processors that do not draw more than 35 W do not require fancy multi-phase voltage regulators. Two or three phases and average output levels are generally enough, and these components also do not get really hot.
Reducing the number of complex components will eventually help to reduce total system costs, as soon as production quantities reach the level of mainstream desktop products. This could be the case as soon as a board design is suitable for desktop, small form factor and other applications - this is why AOpen and DFI decided to go for MicroATX.
At the end of the day, lower power draw will also help to reduce your energy bill quite a bit. Of course this becomes obvious only if the system runs many hours a day or even 24/7. The difference between 120-150 W idle power and 60-80 W is even more impressive if you take into account the possible performance benefits by having two (or more) processor cores.