My concern with the product is its effect on muscle that you don't to grow (eg heart, prostate, toungue [yeah, yeah, save the perverted comments], etc.). In the Biotest article, they said this should not be a concern, but, if memory serves me, they did not explain why. Further, I posted this concern on the t-mag board, which was initially posted but later (with about 15min of being posted) pulled.
The whole scenario did not instill a whole lot of safety confidence in me (assuming it does work, which is, IMO, a very big assumption). Also, I remember reading that Bryan used a myostatin blocker and that he developed some kind of heart issue that subsided after use (irregular beat or something along those lines...try the search if you wanna know about this).
Like I said in my thread on t-mag before it got pulled (such an upstanding company, I tell you), I will let some of you brave guys be the guinea pigs and see if it is safe and if it works.