Just remembered something else. The ballot papers. I know large numbers of people found them particularly confusing. "Mark 1, 2, etc. . . . in order of preference" wasn't the clearest instruction in the world. Moreover, I don't recall at any point anyone explaining how STV worked to the electorate.
There were worrying numbers of spoiled ballots this election. I don't think they could largely have been protest spoilings--especially not with the RON option.