I think the key is that no one knows enough about functional genomes to calculate increasing rates of complexity (as you point out). That is really where the criticism stops for me. I read the paper thoroughly last night and both authors make some great points about how punctuated equilibrium as a concept can't really explain how early life developed so quickly into complex multicellular life. I think you made the point yesterday that there could have been some analogous cambrian explosion that we are unaware of (and may always be unaware of). But evolution of simple replicating chemicals into a RNA world would have taken a tremendous amount of time and we already know that all the comets in Kupier belt are covered with glycine - a crucial amino acid. It is certainly plausible to suspect that life originated pre-Earth. I think the authors made the mistake of a) not going through a proper peer-review channel and b) not being a little more humble with their analysis. They in no way proved that life originated pre-Earth.

However, the most insightful aspect of this paper was not discredited by PZ Meyers analysis at all (and I don't think he read the paper to find out) but they make a compelling argument that the universe may be experiencing a "civilization pulse" over the next 100 million - 1 billion years. I have thought for a while that one of the most compelling answers to Fermi's Paradox is the fact that at the very earliest the universe would have been able to produce an intelligent civilization 10-12 billion years into its evolution. The conditions of the early universe and the length of time it takes for a species like us to evolve would prevent one arising much earlier than that.