Read that too, at what point will it be less effective to use gpus? I got some cpus on PTS running too ^^
Well, nfactor above 12 should render the gpus less effective at mining (considering power consumption). It'll still be faster than cpu, but it won't be worth it. Unless maybe the coin value boosts up like crazy :-P. But even then, I thing a cluster of CPUs would perform better :-)