The Australian dollar rose strongly between 2006 and 2008 as commodity prices rose, which helped to dissipate pressures that would otherwise have caused the economy to overheat. Conversely, the temporary, but sharp, fall in the exchange rate during the recent financial crisis helped cushion the economy on the downside.
Given the consistent way in which the exchange rate has moved to insulate the economy from various external shocks, I would have to conclude that the decision to float the exchange rate in 1983 ranks among the most important economic reforms, if not the most important reform, of the past 30 years.