Well..I won't say snake oil unless I know what's in it chemical wise. I thought the addition of acetone would do nothing for MPG in my Echo, when in fact it did. If these pills contain Acetone, Toulene or Xlene I wouldn't dismiss them as "snake oil", since these 3 are known to help combustion and increase MPG.
EDIT: Ok...I just looked at the MSDS sheets for their products. Only MPG Boost shows what's in it. All others are "proprietary". It contains Xlene. Xlene has been shown to increase MPG and boost Octane. Some people use Xlene to make race fuel. While I can't it would do 7-15% improvement, I have no doubt your fuel economy would benefit from this...I just don't know how much. I'd try it....