50mg is the therapeutic dosage recommended to replace the difficiency seen in men over 30 years old.
Consider it a "life enhancement" and not a "muscle enhancement."
Basically it lets you train like you normally would have if levels had remained the same with age.
Many users see an increase in libido and energy from 50mg, and it is possible to gain muscle faster as well. The way I picture it, is it would allow me to lift and gain the way I could have when I was 18 if I had known then what I know now
I would like to see someone do 100mg.