Its without a doubt that the grey-knights are powerful, in fluff and in crunch. Every Grey-Knight has a storm bolter mounted on their wrist, a nemesis force weapon, and is a powerful psyker, specialized in fighting daemons of chaos. Not a single one of their order has fallen to chaos, and many think this makes them stupid creators-pets. I disagree. While Matt Ward has certainly screwed with them fluff-wise, especially by making them utter psychopaths, (i.E Bloodtide), Kaldor Draigo is pretty damn awesome. Now originally he was definitely a mary-sue, but after 7th edition not so much.