As you have asked I am reporting back after the interview
My first time doing this so I was very happy with the experience at the Perth consulate. Once past security, there were two booths that were active for visa services, one called up people just to take the passport and DS160 front page and the return postage satchel and scanned fingerprints, then you sat back down and got called by another booth later which then the CO there asked your reasons for applying for the visa and all that.
Aside from waiting it was all very quick. Only really asked that I wasn't being going to be paid or employed, or take any course for credit, then asked how I intended to pay, which I said I had savings and would be staying with friends and would have some financial help as well. I couldn't hear him that well through the muffled glass, but seemed to say after that he should approve my visa and expect it to be returned when done (which I'm guessing is 3 weeks to a month typically)
I see a lot of other posts asking you to prove ties to home country but it did not get asked at all. In fact I got an email the day before telling me I had to now bring a letter explaining my purpose and itinerary. I very hurriedly wrote this that night, but at the interview it was never required of me.
I am pretty hopeful that I should get the visa but I am guessing you all know that's never for certain, even if they suggest it should be approved at the interview which was the impression I got. I am now preparing a proper full itinerary, and will look at booking flights (departure and return) as soon as the visa comes back (assuming it does), as I am sure the CBP personnel at whichever airport I arrive at (might be Seattle-Tacoma Intl Airport) will probably want something a lot more substantial than the consulate did, especially if I would be asking for an extension to the usual maximum of 6 months.
As usual if anyone does see any problems or any naïveté on my part please give me any advice you all might have! Would be greatly appreciated as it is the first time I am ever doing something like this.