There are some problems with preferential voting in the Senate though as Antony Green raises (http://www.abc.net.au/news/2013-08-29/green-senate-ballot-sy...).

95% of Australians will defer to their parties' chosen preferences, rather than stating their preferences explicitly. This is mostly because you have to number hundreds of boxes if you chose to vote "below the line".

Some argue that parties' preferences will not always reflect the intention of the voter - but they get away with it because its too difficult to vote preferentially.