To evaluate the effect of protein powders is always difficult as a muscle growth not only from protein powders but also just from the training and the rest of the diet depends. A protein powder alone can do nothing.
I take the powder as a supplement to a protein-rich diet and feel the sport since then something powerful. This can of course also be imagination, but as long as it gives me a good feeling, I'm happy.
Similar digestive problems also has not raised with me the powder.