I agree with Angelo as far as it's safer now than ever before. I live in Potts Point and have done for over 3 years and to be honest I couldn't imagine living anywhere else. I have no fears or concerns for safety walking down the street at night time. Certainly worth coming back and checking it out
No Kings Cross is not a safe area at all, it has never been. Police are everywhere and people still get into fights and brawls. The hospital there is basically designed to treat alcoholic patients and drug abusers, very few other patients actually frequent there. The new laws shut down the place a little early but it's still very rowdy and horrific at night. It's basically our slum in the city, I never go there at night time and I've lived here 15 years. During the day however you'll find that Kings Cross is a really nice place to be, great coffee shops and eateries, friendly people.