having never driven in every state in australia, i cant make a full judgement so i will just comment and vote on the ones i have
ACT: cant drive in suburban traffic, they are always in a rush (which is pointless because it takes you 30 minutes to get from one side to the other in normal conditions and only takes 5 minutes longer in peak hour). they dont understand proper road etiquitte at form one lanes (one left, one right and so on). they are good on highways though, maybe because we dont have any around here and they are too scared to go fast on open roads. canberra drivers seem to be in a daze most of the time.
NSW (sydney): like canberrans, they are always in a rush but because everyone one is used to it it seems to 'work'. they tailgate on major roads. they usually seem alert to what is going on.
QLD (brisbane): good drivers around town/city but terrible on the motorways. tailgate, speed and cut lanes all the time. around town, redlights are just a suggestion
so from my experience i will vote ACT because ther are arse holes and dont know WTF is going on half the time.