A promotion from mastercard & Lufthansa, doesn't seem to have any catches - don't even seem to need to book with your mastercard!
(BTW, if you don't want to leave from Australia - like if you're stopping over somewhere and want to book flights separately, visit http://profero.sg/clients/lufthansa/Q4-Cobranding/ and pick another country, there's actually up to 7% discount from other countries)
Travel the world - with Lufthansa and MasterCard
Save 5% your next flight booking
In cooperation with MasterCard, you can save when making your booking on lufthansa.com. Fly to any of more than 120 Lufthansa destinations in Europe this winter and enjoy 5% off your air fare.
Enter your destination and travel dates in the search form on the right.
Follow the booking process and payment options. The discount is included in the fares displayed.
Terms & Conditions
* Booking Period: 15 November, 2010 to 15 January, 2011
* Travel Period: 15 November, 2010 to 7 April, 2011. Black-out travel dates apply from 22 December 2010 to 10 January 2011.
* Applicable for Economy Class tickets in booking classes L, S, W, V, Q, H purchased on lufthansa.com/mastercardap. 5% discount is calculated compared to published fare level.
* Valid only for flights departing from Australia.
* Discount cannot be combined with any other discounts, promotions or voucher codes. Discount reduces the fare value of the ticket and cannot be applied for fees, taxes, charges or other supplements.
A bit iffy. I tried a route, the new price didn't seem great (it doesn't show calcs), so I tried the regular way just to confirm it worked, and the price that came up was only 2.5% discounted!