Honestly, what will probably happen is the CBP officer will take one look at your passport see that you're Australian, ask you why you're coming to the US, stamp you passport before you can even finish your response, and in you'll go. There's not really a huge problem of Australians migrating to the US illegally.

For residents they do also take your picture with a little webcam type device right at the booth which takes about 2 seconds though I'm not sure if they do that for internationals.

Just stay relaxed, honest if you're questioned about anything, and make sure you have money/credit cards, etc just to show that you're able to fund yourself on the trip in the event that someone asks. There is nothing illegal or questionable about what you're planning to do, so you really have no need to be concerned.