There are 10 countries which enforce compulsory voting and 13 which have it on their books but don't enforcehttp://en.wikipedia.org/wiki/Compulsory_voting
It's a secret ballot, so no one knows if you donkey vote (don't vote correctly and thus have an invalid vote - writing a different name in, scribbling, or a blank vote), you can pre vote the week before, either at a ballot station or fill in a form at the post office, or you can provide an reasonable explanation for not voting (e.g. sick, not in the country).
And I think more Aussies have an attitude of "she'll be right" or "do what you gotta do" and since voting is something that you have to do, most people just shrug, vote, and get on with their day. Our elections really are designed to allow as many people as possible to vote as easily as possible.
I personally, like the compulsory voting system. It gives a more accurate reflection of what the average person wants. It guarantees that the core issues (health, education, police) are always addressed. It means that you don't need to spend millions to get elected to the highest office. And at the end of the day, it means that people are voting in based on their policies and if you don't like the party, don't vote for them.