well, I don't have my copy at hand right now but...
"tainted" cyberware is just stuff that is somehow linked to the Mythos: for example, there's a "R'lyeh Chip" (for those with a neural interface) on the black market that will transform the VR environment of the net into a surreal underwater landscape - complete with mysterious ancient ruins etc. However, some users are rumored to have simply vanished after using this chip...
I have run a *very* successful GURPS Cthulhupunk campaign for about 3.5 years - and all I can say is: go for it!
(unless, of course, you are ready for the next level: then get yourself Transhuman Space - and start a "Transyuggothian Space" campaign...)