When you do the calculations, as long as the interest rate you get by putting money in the bank sufficiently exceeds the indexing interest rate then you're better off deferring to HECS than getting the 10% discount when considering opportunity costs (might be a slightly different story if the discount was 20% like it was back when I started). Assuming your income grows substantially every year through career progressions, the HECS debt should be wiped off in about 10 years or so with compulsory repayments only.
However, this assumes that there will be no significant reforms to that HECS scheme for the duration of the debt. The federal government's now failed proposal a while back to change the indexation on all existing debts to the government bond rate rather than inflation was a bit of a scare because the government bond rate is generally closer to the interest rate your bank offers than the inflation rate, thereby reducing that benefit in deferring. Hopefully the HECS scheme won't change dramatically in the near future.
