I was thinking about Shadowrun when I read this the first time and I "think" they had something about the bodies rejection of cyberware. Mostly I think they pumped the body full of meds to add in the healing process and to subdue alot of the bodies reaction to something foreign.
But come to think of it the body might not care much at all. Maybe people work around with piece of glass, shrapnel and so on from wars and accidents within their bodies, which isnt pushed out. I also read in a scientific magazin once about a person who many times pushed a blade through his abdomen. Since he had done it so many times, the body simply had made a tunnel of scartissue, which would never close. There is also the example of hipreplacements, they arent as far as I know rejected either.
The problem might lie in the area of the nerve interfaces, but actually I dont think there would be a problem, come to think of it.
Long post to agree with Defendi