We here at the Logic Design blog seem fascinated with improving design metrics. Why is that? Perhaps we've seen too many designs go through "long loop" iterations later in the cycle because improper metrics were used to determine the design's "goodness" early in the cycle.
Anyway, ARM announced the Cortex M0 processor today, a power-efficient low-cost processor targeted for medical devices, smart control, lighting, gaming accessories....you know, all the things that everybody says will drive growth in the electronics industry in the coming years. What enables that? Power efficiency - performance-per-watt. This core consumes "as little as 85 microwatts/MHz". (We'll ignore the "as little as" for now...we know this is going to be dependent on the activity).
Performance-per-watt, or milliwats-per-megahertz, however you want to name it - should be a metric that every chip designer looks at today. You can optimize for one factor in the equation or both, but at the end of the day this top-level metric gives a good indication as to how "green" your design really is.