Do people take advantage of instant run-off voting to "not throw away their vote"?

What do they do in Australia? Where else do people have such systems? I suppose I could just look up Australia, but I fear it might be hard to interpret and I’d rather hear from someone with experience of it.

I ask because the recent British Labour leadership election was very different from the last. I suspect that there was a substantial portion of the electorate who preferred, say, Abbot in 2010, but didn't vote for her because she was not viable. The whole complicated system exists to allow people to simply express their preferences and not put in the strategic voting effort of determining who is viable, but maybe it isn't doing much.

(It is definitely doing something. In 2010, 28% of the vote share went to non-viable candidates. A plurality system applied to those first round votes would have chosen David over Ed.)