In my own opinion, looking at myself and others who have used. I wouldnt recomend the use until you are at least 10% or lower b/f. Most people who use want to have the full ripped look, and you are not going to show that until you are around 10% or lower. I myself am at 7 - 8%, the lower you are at b/f the less bloat, at least that is what I have seen, it also probably goes hand in hand with proper diet and water intake.
The people with higher b/f at the gyms I have worked out at of course get bigger, but they always look bloated (balloon affect), thus they wind up doing more cardio and killing off more muscle.
As one of my power lifter frineds who give me advice says to me, if you are trying to build, dont do cardio, hell dont even walk fast! Cut down first, then do your bulking, it has worked wonders for me, and the guys I work out with. It might be harder to do this way, but the results are amazing!!!