The only negative with Sustanon is that it is made up of 4 different esters, therefore blood levels bounce up and down haphazardly during the cycle...
It contains a small amount of Prop, which is in and out of your system rapidly, and then the other esters keep running so therefore the amount of Test in your system is lower until your next pin. Managing estradiol can be even more difficult because of this.
Obviously if your source is trustworthy, then of course you will make decent gains on Sustanon - but I'd certainly advise Enanthate or Cypionate for a much smoother run with less peaks and troughs.