As someone who has worked in both systems (Australian and US), some thoughts:
Australian house officers (junior residents) do not routinely "make $100,000" per year. Base salaries tend to range between $65 and $75K AUD per year. This data is easily available on-line.
While Australian house officers do earn overtime, most hospitals have strict policies about avoiding this. We always had to watch the clock closely because we were instructed that overtime was frowned upon and that the hospital did not wish to pay it.
There is no right or wrong way to do it; longer training schemes in Australia with shorter hours are what Australians are used to. You poll Americans and they wish to work longer hours for shorter periods of training; its what we are used to. To each his own. But there is no doubt that the average Australian and average American are different. Americans work longer hours, take less vacation, etc. A friend of mine, a psychiatrist in Sydney, vacations several times a year and "wouldn't feel comfortable being gone for more than a month at a time". Most American physicians wouldn't feel comfortable being gone for more than 2 weeks given the demands of patients here.
The major issue I have with the Australian training is the amount of subjectivity there is in advancing someone from HO to Registrar and finishing specialist training. On more than one occasion I observed a Registrar anger a Consultant and having that result in additional training required (ie, adding on a year to their training).
In comparing house officers between the 2 countries, I find that Australian physicians tend to be better clinically but many lack in depth knowledge of tests performed/basic science that US junior residents have. However, at the completion of training, I see no difference between the 2 countries.
I've worked as a resident prior to the US work hour restrictions and I can verify that not all of those triple digit work weeks were filled with educational experiences. But there has to be a breaking point at which the hours worked:education becomes unfavorable. I don't know what that number is. The problem with stating "I work 40 hours a week and feel comfortable with my knowledge" is that we generally are not the best judge of such things. You don't know what you don't know.
Lastly, as L2D notes, its not really fair for anyone to judge another's idea of paradise/appropriate work hours. My life might be wonderful or boring in another's eyes, but what matters is what I think.