I see this topic could get hot again. But here is my experience. Since using solely optimax for the past 3 months, I average 3-4 mpg more than before. There, was a noticable difference in performane within the first tank, and improved more after several more tank fulls went through the engine. Torque and responsiveness, have noticably improved too.
This is certainly no placebo, as regular just seems to sap its will to drive compared to the good stuff.
Maybe my car is more atuned to this type of fuel than others. But if you are in any doubt - try it for yourself. If you dont like it then just go back to your old fuel. I know I'm going to stick with it.