Well, in Augmentation on page 94 it says that if you get 5 hits on your Edge test then "The infusion integrated perfectly. The character gains the full effects (Emphasis mine)of the infusion as a permanent modification at a cost of 0.4 Essence." In the flavour text on page 93 it says, "The best outcome is that the geneintegrates perfectly in the genome and the character recieves all of the intended benefits of the infusion as a permanent enhancement."
None of this says that you do not gain the downsides of the infusion. Is there an official answer to whether or not a permanent infusion gives you only the benefits or if you get the nasty downsides as well? Considering it costs you essence I am inclined to say it's "con free," but it is not 100% clear. They left that little hint of doubt with this omission.