I searched through Shane's videos and this forum, but found nothing on the subject. For, or against, Instant-Runoff Voting? I've heard only good arguments for it and thus far support it. I don't really know what the downsides to it would be. It certainly seems better than plurality voting.
IRV is problematic in that, once a candidate is eliminated, he can't come back. So if only half of the population approves A as first choice, and half approves B, but they ALL approve C as second choice, C becomes eliminated and doesn't get elected--even though everyone wants him as a second choice.
The Condorcet method fixes this. There's also approval (or range) voting, which is a lot simpler yet solves many of the same problems.