[sergsz]

Jman,
I think your assertion that a 50% reduction in "edge" leads to a more than 50% reduction in ROI is accurate and very perceptive. However, for your assertion to have practical value, it would also have to be true that players could accurately estimate their edge (or change in edge) based simply on "feel." I don't think that this is actually the case. I could say that I feel I have a slightly smaller edge in Speeds than in Regulars, but if I try to say that this reduction in edge is 40% or 50% or whatever based simply on feel, I am likely talking out of my ass. The only way to accurately quantitatively assess the difference in edge between two formats is to play a large sample size of each and compare the ROIs. At which point, ZSROI stops being a useful concept because because normal ROI is sufficient for determining which format is more profitable.