Hey Godslayer,
What do you like doing? Beach? Wineries? Wildlife? Bush (nature) walking? Sport? Arts? Shopping? Are there any children coming with you?
Nemo makes a great point... what do you want to do with your time?
Australia is the oldest landmass on earth. It has some unique natural beauty. There is a lot to see. But be forewarned: Australia is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to Australia. If you want to see some of her natural wonders, prepare to lose several days to travel.
"Australian" food can be so many things... it could be indigenous bush tucker... food prepared with native flora or fauna (kangaroo, emu, crocodile, barramundi)... or pre-contemporary stereotypes (damper, ANZAC biscuits, lamingtons, pavlova). Australia is one of the most multicultural countries in the world - so "Australian" food is similarly culturally diverse. To me, this is what makes Australia's food culture special. Australia must be close to the top (if not at the top) of a small list of countries who have a wide range of decent Asian and Mediterranean food. If you aren't chasing fine-dining, most of these options are good 'stick to your ribs' meals that can be had at fair prices.
Drinks: Australia has a serious tea and coffee culture. Most blocks in Sydney & Melbourne CBD will have an independent cafe (or several) capable of making decent espresso coffee. Australian wine is good, though it may not seem exotic as it is heavily exported. Don't equate the stereotype of Australians drinking beer until they chunder with Australian beer being good. The big labels are not terrible nor are they fantastic. Plenty of good import beers will be available and the trend towards craft beers has also provided some good options.
A last note on food at the shops and restaurants... by global standards it is relatively expensive. Travellers will likely be amused and annoyed by the price locals are willing to pay.