Just back from sydney and happy to contribute (just no arguing), although I am itching to reply to Rooflyer.
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No problems with sandals at all - did examine the pictures at the airport and my sandals are clearly within allowable guidelines as probably are sandals without a back strap! all too hard! I couldn't see a mention of a tracksuit as not being allowed, but when I was chatting to the lady at the desk in the business lounge she said tracksuits would only be allowed if worn as part of a sports team uniform. Incidentally she thought it was all very silly and wasn't looking forward to enforcing it.
Another thought - nowhere on the Qantas site as part of the blurb on domestic business class tickets are the rules mentioned. Only as part of the Qantas club access, so Qantas either needs to update that info, or allow people accessing the lounge as part of class of service to wear thongs