Are you sure???
Simon, not sure if you have spotted something that I haven't, but BP2 (http://www.budget.gov.au/2013-14/content/bp2/html/bp2_revenue-10.htm) indicates that the monthly PAYG arrangements will apply to large entities (with a turnover >$20m) from 2017. This may not affect too many individual IT contractors.
Possibly more significant for contractors is the introduction of a cap on tax deductions for work-related self-education expenses (further down on the same page) - a $2,000 cap would limit the ability of many IT contractors to claim deductions for IT related training.
(Beer, because reading budget papers always induces thirst).