Walked around at night pretty late. Went to a jazz club with colleagues. Took the trolleys around and walked a ton at all times of day. It was dirty and at times smelled worse then some third world countries I have visited. Never felt at risk of danger. Parts of the city are gorgeous and the food is amazing.
That said I can't imagine going to NO for vacation. It's built for drinkers and partiers. Not really a ton of family stuff unless you plan to visit the plantations and the bayou for a air boat trip. I don't plan to ever go back unless someone else is paying.