The most frequent question we've received since our return from Australia has been some variation of, "Is it difficult driving on the left side of the road?"
The answer: Not really. Australia was, in fact, the second time in the past few years we've had to drive on the left side; we rented a car in Scotland a couple of years ago, too.
Sure, you frequently have to remind yourself that you need to be in the left lane when pulling out of a driveway first thing in the morning - and you may occasionally catch yourself trying to get into the right lane. And yes, the gas and brake pedals are backward.
But once you get going, it's not really that difficult. No matter which side of the road you're on, the driver is always in the middle.
The hardest part, for us at least, was signaling turns. The turn signal and windshield wiper levers are also reversed, and for some reason that tripped us up the most. It also was the hardest thing to readjust to when we returned home and started driving our own car.
The best piece of advice I received about driving on the left side was to rent an automatic. Cars with sticks can be cheaper, but with an automatic it's one less thing to worry about.
Fortunately, because we parked the car in Melbourne and walked or took the tram, we never encountered what appeared would be the biggest obstacle to driving in Australia: the "hook turn" in Melbourne. I won't even try to describe it, so here's a description.