To be fair, Australia has two conservative parties, rather than only one. They are very similar, but that’s something.
They say it ends the spoiler effect; and it kind of does with only two strong candidates. Most voters aren’t forward-thinking enough to look to a future with three or more strong candidates.
I think evidence is mixed on whether IRV reduces partisan mudslinging. The exorbitant figures that are spent on negative ads in Australian politics suggest that the effect is limited beyond the local level at best.
At the end of the day, these kinds of organizations need more evidence that 1) your voting system is good and 2) it has volunteers working for it. I think St. Louis is a major steal for the 2nd point, given how big it is (check out the fact they got 2,000 signatures in 3.5 months, though they still need another 18,000), and for the first point, we unfortunately have to wait a while longer. Maybe take that poll CES put out the other day showing Elizabeth Warren had 85% support from NetRoots visitors?