Instant run-off voting, aka Alternative Vote is just better in every aspect than the "first past the post" (FTFP) system, Strife. It doesn't mean doing away with the two parties, but it means there's room for a third one to grow. It's functionally identical to the regular system, where you put a "1" next to a candidate's name, however you can put e.g. a "2" next to a second candidate's name, and if your first choice gets knock out, your vote transfers to person #2 (and so on). It removes the "spoiler effect", which allows third parties to run candidates without being accused of splitting the vote. You still end up with two main parties, but third parties could get more say, at local and state level, and federally, especially in the senate.
There's basically no downside to the Alternative Vote compared to First Past The Post. And it gives more feedback. Say, the Democrat candidate gets 35% of the vote, the republican gets 45% too, and the local Greens candidates gets 20%, with those 20% of voters putting the Democrat as their #2 choice. If it was "first past the post" the republican would have won, even though more people favored the Democrat, or Green voters would have voted strategically (i.e. not voted for their first-choice "Greens" candidate at all, since that would hand the election to the Republican).
This distorts people's true voting intentions, and loses information in the process unnecessarily. FTFP prevents people from voting for who they really want to, and if they vote for who they really want to, it prevents the election of a candidate that the majority would actually prefer. However, with Alternative Vote, it's public knowledge that 20% of people's true first choice was Green, and this creates more information in the system -it lets elected officials know that people in that area really care about Green issues. Those concerns are invisible when the choice is merely Fascist A and Fascist B ;P