I consider it safe, but there are some caveats.
1) Keep in mind that, as an enterprise, they want revenue coming their way.
2) As an Australian, you are way behind Americans and British people in acceptance by the companies. You won't get as much offers, and credits.
3) I once formulated: "Get used to the feeling of becoming scammed," meaning that there is an impression that they tend to take more than they give. We've heard a lot here of broken connections and impossible communication, leading to less credits awarded than expected.
4) Other ways? I'm unpopular for this opinion, but honest labour leads to honest money to buy those credits. My opinion on "free credits": The (expected) outcome of 200 cr per hour would cost me too much of my precious lifetime. I'd rather limit my spendings if necessary.