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.
Fitnesses are dependent on the environment, though. So: if agent A has goal GA, B has goal GB and C has goal CG, and A and B produce GA, B and C produce GB and C and A produce GC then you can't just assign scalar fitnesses to each agent and expect that to work. That could happen with circular predation, for example.
If you do want to assign scalar fitnesses to organisms - in order to compare them - I think you have to do something like testing them on a standard suite of test environments.