My major concern about IRV is that there's a lot of false promises made with it. It is shown (and we have real world examples) that it doesn't do a great job at removing spoilers, which I think is most peoples' number one draw to the system. It also doesn't scale very well and becomes less transparent as it does so. That's why I personally reject the push for ordinal systems and push for cardinal. This may seem absurd, but we've had IRV in the US in the past and we reverted back to plurality. So there's historical precedence for this position as well.