If your booking $500 or more of anything at STA (or planning to) before 31st March then its worth grabbing the voucher and getting the discount.
Conditions on the voucher - Must be presented at the start of the consultation process. Valid for international travel departing Australia. Valid on all new confirmed airfare bookings made in conjunction with a minimum of $500 worth of accommodation, touring and/or travel insurance. Not to be used in conjunction with any other offers. Not redeemable for cash. Non refundable if part used. Valid in store only. Must be used before 31st March 2013