I am not going to come out so strongly opposed to it. Maybe it is too good to be true.
However, I think there is a certain "anti-supplement" bias on this forum. People post questions about First Endurance products and EAS products all the time and hardly anyone ever responds. I strongly believe many people have tried them and are currently using them but don't want to say so for fear of people saying "Oh, well that's why you placed X in Y race."
I used Optygen 2 years ago and had some great training, yes there were other variables, but they were few as I am a pretty routine based person. If it wasn't for the price I will use it still.
Portside Athletics Blog