I agree. It is the task of the intelligence to decide how "efficiently" will solve a particular task. A greater intelligence may decide to pack it together with some other problems and to solve it that way, many at once. It's less efficient form the point of view of this problem, but not from a broader perspective.
It is also not always that the time what's crucial, maybe the energy spent or the nerves of the boss spared or something else.
The more and the stronger motives served, would be a better definition of a greater intelligence.
Suppose agent A has goal G, and agent B has goal H (assumed to be incompatible). Put both agents in the same world. If you reliably end up with state G, then we say that A has greater optimization power.
I guess there's a hypothesis (though I don't know if this has been discussed much here) that this definition of optimization power is robust, i.e. you can assign each agent a score, and one agent will reliably win over another if the difference in score is great enough.
If the world is complex and uncertain then this will necessarily be "cross-domain&q...
Anna Salamon and I have finished a draft of "Intelligence Explosion: Evidence and Import", under peer review for The Singularity Hypothesis: A Scientific and Philosophical Assessment (forthcoming from Springer).
Your comments are most welcome.
Edit: As of 3/31/2012, the link above now points to a preprint.