Roger, at least at first blush, seems to be a divergence between your view of benefits clamed for pressure regulators, especially considering your statement as follows:
"Claims for any significant performance improvements or differences in fuel consumption due to the use of a pressure regulator valve rather than a needle valve are total crap and hogwash, or extreme marketing spin. Or worse."
compared with Will Rietvelds's review last fall of the Jetboil Sol, describing its "thermo-regulate" technology as a benefit worth noting:
"Besides being lightened throughout, they incorporate the new Jetboil Thermo-Regulate™ Technology, which is a pressure regulator that maintains burner output as the fuel in the canister diminishes and improves performance in temperatures down to 20 F (-6 C)."
Excerpt from http://www.backpackinglight.com/cgi-bin/backpackinglight/sotm11_jetboil_sol_advanced_review.html
Maybe just a matter of degree of "improved performance" and defining what amounts to a "significant" improvement?
Or maybe the pressure regulator technology that you're analyzing is not the same technology used in the Jetboil?
I'm not an expert, or even an informed "pressure regulator" person, but it just seemed like there was a huge difference between what Will concluded (it's a benefit) and what you find (it's "total crap and hogwash").
PS -- I very much appreciate your tech articles, especially with all the extremely helpful pictures, charts, and diagrams.
PPS -- To drift a bit, why is it (as you've said elsewhere) that the Gnat has good CO levels when there's evidently a narrow space between the burner and the bottom of a pot resting on the pot supports? Thought that distance between pot bottoms and burners was a big factor for CO levels, with a lesser distance causing an increased CO level. And to make this "drift" semi-relevant, does a pressure regulator have any effect on CO levels, up or down?