Out of curiosity, what ARE the benefits of being tied to England? All I can think of is the Commonwealth Games. 
In a nutshell:
That, and I'm sure it will pain most Aussies to see England topping the medal tallies once we're gone. Where's the competition for England once we're gone? It also serves as good training for the Olympics.
Also, I believe it's too expensive
1 to become a republic at the moment. Money should be better spent in my opinion with so much going on in the world.
I'm a strong believer of
"If it ain't broke, don't fix it." There's nothing wrong with staying as a constitutional monarchy - in fact, we were head over heels when Prince William came to Australia.
1=
http://www.statusquo.org/cgi-bin/republic_cost.cgihttp://www.norepublic.com.au/index.php?option=com_content&task=view&id=649&Itemid=35EDIT: I know the two sites I've given are very pro-monarchy, but they should be used as an estimate because I'm sure some figures may have been blown out of proportion knowing its source.
And also, for the pro-republicans, please feel more than free to convert me.