In the studies, 1mg/kg for the mice equates to about 4 grams to achieve the same effects (60% increase in a 200-210 lb male) in a human male so 1mg at one time is actually not that bad. One gram would give you roughly a 15% increase in muscle mass. There were also no observed side effects to the mice at that dosage, and the effects continued for about 2 weeks after the last dose. I can definitely say the stuff works as I have now tried it myself. I have a log of what I did over at MC and my reasoning behind it (under the same username). There are weekly progress pictures so you can decide for yourself if it really works. Just posted this week's picture.
Prior to using follistatin, I used acvr2b back in September, 2010--another myostatin inhibitor. I was able to obtain it directly from a biochemical company that produces it so it was the real thing. I posted what I used, results, and progress pictures from that little experiment as well.
I haven't had any kind of side effects at any time while using follistatin, myostatin pro-peptide, or acvr2b. The only thing "bad" that happened to me was that I ripped a shirt sleeve yesterday (really, and I'll post the pic I took of it if I have to).