Honestly I have been living in Brisbane for several years and I have had no problems. There are no rednecks here but there are bogans and yobbos, that is a term for an unsophisticated Aussie, they are actually harmless and occasionally entertaining. This one guy, his motorbike caught fire and he tried to put it out by throwing whiskey on it, crazy stuff but no harm or evil intended. Sydney also has a lot of very rough areas, when I visited a couple of years ago, a middle aged man was stabbed to death near a pie shop by two teenagers. Some gang also exploded a small bomb at a rugby match in Sydney, no one got hurt but it scared the hell out of people, there was also some disgruntled supermarket worker after being injured in robbery at gunpoint, he threatened to blow up the store but wound up setting his own house on fire, the police found explosives in his apartment. So please get the idea that Sydney is Disneyworld out of your head.
Redfern and King's Cross are pretty shady areas, KC has a lot of prostitution and other bad elements. They are like the Aussie version of the ghetto. Still there are plenty of nice areas in Sydney.
For the most part its a nice city but it does have some problems like most major cities.