yeah man khan is a great fighter, in every category. The only thing is his chin. But if he fights the way he's been doing, keeps that chin tucked in and keeps his guard up he'll be fine.
Plus, I believe that now that he spars against pacquiao on the regular, and welterweights and middleweights i.e bigger stronger guys, that toughens you up and does improve your chin. Back in the UK before Roach, he was sparring against stiffs and wasn't really allowed to get hit, and that showed in his fights. He's better now and he's only 23 so he can keep improving.