those models = pure concentrated awesome. An'ggrath the unbound is everything a khorne player could want in an army centre piece and Zarakynel is a thousand times better that the GW keeper of secrets model. Scabiathrax is just grusomeness made model and i love it, i mean his spine is sticking out and stuff.
The special rules for these deamons are insane. The new forge world apocalypse realeased ones are a bit tamer but still nasty. You could of course now field them as generic (ala crap) 'greater deamons' but there is no way that would do them any sort of justice.